Android buildbot: be more tolerant of 'stuck' devices.
Android buildbot: be more tolerant of 'stuck' devices.

Be explicit about which device we are 'wait for boot'ing on.  Also add
explicit timeout on wait-for-boot.

BUG=None
TEST=


Review URL: http://codereview.chromium.org/8831002

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@113363 0039d316-1c4b-4281-b951-d872f2087c98

gavinp/chromium,yitian134/chromium,gavinp/chromium,adobe/chromium,gavinp/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,ropik/chromium,gavinp/chromium,adobe/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,adobe/chromium,yitian134/chromium,adobe/chromium,adobe/chromium,yitian134/chromium,yitian134/chromium,adobe/chromium,gavinp/chromium,gavinp/chromium,yitian134/chromium,yitian134/chromium,ropik/chromium,ropik/chromium,ropik/chromium,yitian134/chromium,gavinp/chromium,ropik/chromium,yitian134/chromium,adobe/chromium,ropik/chromium,ropik/chromium,adobe/chromium,adobe/chromium,adobe/chromium,gavinp/chromium,yitian134/chromium