Fix executable searching in keygen.py
Fix executable searching in keygen.py

Add the script's directory to the search path, so it can be used in a
standalone tarball for Virtual Me2Me.

Use os.path.join() instead of string concatenation.

Make the module safe to import (that is, don't search for remoting_host_keygen
whilst the module is being imported, because it fails to work from tools such
as pychecker etc).

BUG=None
TEST=Manual

Review URL: http://codereview.chromium.org/9114045

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@117104 0039d316-1c4b-4281-b951-d872f2087c98

patrickm/chromium.src,dushu1203/chromium.src,jaruba/chromium.src,littlstar/chromium.src,keishi/chromium,dednal/chromium.src,patrickm/chromium.src,ondra-novak/chromium.src,robclark/chromium,chuan9/chromium-crosswalk,Jonekee/chromium.src,dushu1203/chromium.src,anirudhSK/chromium,zcbenz/cefode-chromium,mogoweb/chromium-crosswalk,Jonekee/chromium.src,krieger-od/nwjs_chromium.src,hgl888/chromium-crosswalk,Jonekee/chromium.src,patrickm/chromium.src,timopulkkinen/BubbleFish,mohamed--abdel-maksoud/chromium.src,krieger-od/nwjs_chromium.src,patrickm/chromium.src,keishi/chromium,nacl-webkit/chrome_deps,axinging/chromium-crosswalk,timopulkkinen/BubbleFish,rogerwang/chromium,pozdnyakov/chromium-crosswalk,krieger-od/nwjs_chromium.src,Fireblend/chromium-crosswalk,Just-D/chromium-1,Pluto-tv/chromium-crosswalk,hgl888/chromium-crosswalk,chuan9/chromium-crosswalk,littlstar/chromium.src,ondra-novak/chromium.src,hgl888/chromium-crosswalk-efl,dushu1203/chromium.src,axinging/chromium-crosswalk,littlstar/chromium.src,anirudhSK/chromium,robclark/chromium,dushu1203/chromium.src,zcbenz/cefode-chromium,keishi/chromium,hgl888/chromium-crosswalk,timopulkkinen/BubbleFish,PeterWangIntel/chromium-crosswalk,rogerwang/chromium,crosswalk-project/chromium-crosswalk-efl,crosswalk-project/chromium-crosswalk-efl,timopulkkinen/BubbleFish,crosswalk-project/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,dednal/chromium.src,ChromiumWebApps/chromium,zcbenz/cefode-chromium,hujiajie/pa-chromium,chuan9/chromium-crosswalk,pozdnyakov/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,nacl-webkit/chrome_deps,ChromiumWebApps/chromium,fujunwei/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,hujiajie/pa-chromium,pozdnyakov/chromium-crosswalk,Chilledheart/chromium,timopulkkinen/BubbleFish,zcbenz/cefode-chromium,zcbenz/cefode-chromium,M4sse/chromium.src,mogoweb/chromium-crosswalk,markYoungH/chromium.src,ltilve/chromium,jaruba/chromium.src,Fireblend/chromium-crosswalk,TheTypoMaster/chromium-crosswalk,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,hgl888/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,krieger-od/nwjs_chromium.src,hujiajie/pa-chromium,ChromiumWebApps/chromium,jaruba/chromium.src,crosswalk-project/chromium-crosswalk-efl,rogerwang/chromium,robclark/chromium,pozdnyakov/chromium-crosswalk,pozdnyakov/chromium-crosswalk,anirudhSK/chromium,TheTypoMaster/chromium-crosswalk,Just-D/chromium-1,PeterWangIntel/chromium-crosswalk,nacl-webkit/chrome_deps,littlstar/chromium.src,chuan9/chromium-crosswalk,Pluto-tv/chromium-crosswalk,bright-sparks/chromium-spacewalk,M4sse/chromium.src,timopulkkinen/BubbleFish,Jonekee/chromium.src,ChromiumWebApps/chromium,PeterWangIntel/chromium-crosswalk,M4sse/chromium.src,robclark/chromium,hujiajie/pa-chromium,anirudhSK/chromium,axinging/chromium-crosswalk,rogerwang/chromium,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,keishi/chromium,crosswalk-project/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,nacl-webkit/chrome_deps,hujiajie/pa-chromium,chuan9/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,nacl-webkit/chrome_deps,jaruba/chromium.src,timopulkkinen/BubbleFish,krieger-od/nwjs_chromium.src,Jonekee/chromium.src,zcbenz/cefode-chromium,junmin-zhu/chromium-rivertrail,hgl888/chromium-crosswalk-efl,krieger-od/nwjs_chromium.src,robclark/chromium,zcbenz/cefode-chromium,mohamed--abdel-maksoud/chromium.src,mohamed--abdel-maksoud/chromium.src,hujiajie/pa-chromium,Pluto-tv/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,dushu1203/chromium.src,fujunwei/chromium-crosswalk,hujiajie/pa-chromium,hgl888/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,ltilve/chromium,junmin-zhu/chromium-rivertrail,crosswalk-project/chromium-crosswalk-efl,fujunwei/chromium-crosswalk,jaruba/chromium.src,Fireblend/chromium-crosswalk,Pluto-tv/chromium-crosswalk,chuan9/chromium-crosswalk,mogoweb/chromium-crosswalk,ondra-novak/chromium.src,markYoungH/chromium.src,anirudhSK/chromium,hujiajie/pa-chromium,junmin-zhu/chromium-rivertrail,mogoweb/chromium-crosswalk,hgl888/chromium-crosswalk-efl,M4sse/chromium.src,markYoungH/chromium.src,bright-sparks/chromium-spacewalk,dushu1203/chromium.src,markYoungH/chromium.src,jaruba/chromium.src,hujiajie/pa-chromium,ondra-novak/chromium.src,hgl888/chromium-crosswalk,mogoweb/chromium-crosswalk,jaruba/chromium.src,ondra-novak/chromium.src,hujiajie/pa-chromium,chuan9/chromium-crosswalk,bright-sparks/chromium-spacewalk,robclark/chromium,timopulkkinen/BubbleFish,mohamed--abdel-maksoud/chromium.src,Jonekee/chromium.src,Pluto-tv/chromium-crosswalk,axinging/chromium-crosswalk,keishi/chromium,ltilve/chromium,ltilve/chromium,Pluto-tv/chromium-crosswalk,ChromiumWebApps/chromium,timopulkkinen/BubbleFish,robclark/chromium,mohamed--abdel-maksoud/chromium.src,dushu1203/chromium.src,fujunwei/chromium-crosswalk,keishi/chromium,Chilledheart/chromium,pozdnyakov/chromium-crosswalk,junmin-zhu/chromium-rivertrail,Chilledheart/chromium,M4sse/chromium.src,axinging/chromium-crosswalk,bright-sparks/chromium-spacewalk,ondra-novak/chromium.src,mohamed--abdel-maksoud/chromium.src,Just-D/chromium-1,anirudhSK/chromium,Just-D/chromium-1,crosswalk-project/chromium-crosswalk-efl,markYoungH/chromium.src,Pluto-tv/chromium-crosswalk,ondra-novak/chromium.src,dednal/chromium.src,TheTypoMaster/chromium-crosswalk,junmin-zhu/chromium-rivertrail,mohamed--abdel-maksoud/chromium.src,ondra-novak/chromium.src,hgl888/chromium-crosswalk-efl,Chilledheart/chromium,Chilledheart/chromium,dednal/chromium.src,rogerwang/chromium,jaruba/chromium.src,rogerwang/chromium,TheTypoMaster/chromium-crosswalk,Chilledheart/chromium,crosswalk-project/chromium-crosswalk-efl,markYoungH/chromium.src,nacl-webkit/chrome_deps,junmin-zhu/chromium-rivertrail,M4sse/chromium.src,ChromiumWebApps/chromium,timopulkkinen/BubbleFish,hgl888/chromium-crosswalk-efl,junmin-zhu/chromium-rivertrail,bright-sparks/chromium-spacewalk,zcbenz/cefode-chromium,dednal/chromium.src,dednal/chromium.src,dednal/chromium.src,M4sse/chromium.src,markYoungH/chromium.src,anirudhSK/chromium,Fireblend/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,rogerwang/chromium,Jonekee/chromium.src,PeterWangIntel/chromium-crosswalk,Just-D/chromium-1,hgl888/chromium-crosswalk,keishi/chromium,M4sse/chromium.src,dednal/chromium.src,axinging/chromium-crosswalk,bright-sparks/chromium-spacewalk,littlstar/chromium.src,patrickm/chromium.src,ChromiumWebApps/chromium,rogerwang/chromium,hgl888/chromium-crosswalk-efl,mogoweb/chromium-crosswalk,jaruba/chromium.src,TheTypoMaster/chromium-crosswalk,anirudhSK/chromium,Fireblend/chromium-crosswalk,nacl-webkit/chrome_deps,robclark/chromium,ltilve/chromium,pozdnyakov/chromium-crosswalk,PeterWangIntel/chromium-crosswalk,anirudhSK/chromium,littlstar/chromium.src,markYoungH/chromium.src,keishi/chromium,M4sse/chromium.src,TheTypoMaster/chromium-crosswalk,dednal/chromium.src,TheTypoMaster/chromium-crosswalk,M4sse/chromium.src,ltilve/chromium,patrickm/chromium.src,axinging/chromium-crosswalk,Fireblend/chromium-crosswalk,markYoungH/chromium.src,patrickm/chromium.src,M4sse/chromium.src,hgl888/chromium-crosswalk,rogerwang/chromium,pozdnyakov/chromium-crosswalk,junmin-zhu/chromium-rivertrail,ChromiumWebApps/chromium,keishi/chromium,bright-sparks/chromium-spacewalk,pozdnyakov/chromium-crosswalk,Jonekee/chromium.src,Fireblend/chromium-crosswalk,mohamed--abdel-maksoud/chromium.src,dushu1203/chromium.src,mohamed--abdel-maksoud/chromium.src,nacl-webkit/chrome_deps,hujiajie/pa-chromium,Chilledheart/chromium,Just-D/chromium-1,patrickm/chromium.src,keishi/chromium,dushu1203/chromium.src,fujunwei/chromium-crosswalk,fujunwei/chromium-crosswalk,bright-sparks/chromium-spacewalk,markYoungH/chromium.src,chuan9/chromium-crosswalk,fujunwei/chromium-crosswalk,axinging/chromium-crosswalk,anirudhSK/chromium,zcbenz/cefode-chromium,Pluto-tv/chromium-crosswalk,markYoungH/chromium.src,mogoweb/chromium-crosswalk,Fireblend/chromium-crosswalk,chuan9/chromium-crosswalk,dednal/chromium.src,dushu1203/chromium.src,zcbenz/cefode-chromium,rogerwang/chromium,ChromiumWebApps/chromium,krieger-od/nwjs_chromium.src,ChromiumWebApps/chromium,junmin-zhu/chromium-rivertrail,robclark/chromium,krieger-od/nwjs_chromium.src,littlstar/chromium.src,dednal/chromium.src,pozdnyakov/chromium-crosswalk,pozdnyakov/chromium-crosswalk,ChromiumWebApps/chromium,littlstar/chromium.src,Just-D/chromium-1,mogoweb/chromium-crosswalk,patrickm/chromium.src,ltilve/chromium,hgl888/chromium-crosswalk,robclark/chromium,bright-sparks/chromium-spacewalk,PeterWangIntel/chromium-crosswalk,Jonekee/chromium.src,zcbenz/cefode-chromium,jaruba/chromium.src,axinging/chromium-crosswalk,axinging/chromium-crosswalk,ondra-novak/chromium.src,nacl-webkit/chrome_deps,anirudhSK/chromium,hgl888/chromium-crosswalk-efl,Chilledheart/chromium,nacl-webkit/chrome_deps,junmin-zhu/chromium-rivertrail,crosswalk-project/chromium-crosswalk-efl,jaruba/chromium.src,TheTypoMaster/chromium-crosswalk,nacl-webkit/chrome_deps,Jonekee/chromium.src,Jonekee/chromium.src,hgl888/chromium-crosswalk-efl,ltilve/chromium,mogoweb/chromium-crosswalk,timopulkkinen/BubbleFish,Chilledheart/chromium,anirudhSK/chromium,ChromiumWebApps/chromium,hgl888/chromium-crosswalk-efl,keishi/chromium,ltilve/chromium,mogoweb/chromium-crosswalk,junmin-zhu/chromium-rivertrail,dushu1203/chromium.src,Just-D/chromium-1,Pluto-tv/chromium-crosswalk