Print error if nova-manage should be run as root.
Print error if nova-manage should be run as root.

Fix bug 939531.

This patch makes nova-manage print out a more friendly error message if
it needs to be run as root instead of failing with an exception
traceback.  It catches an EACCES error when opening the config file or
opening log files and exits cleanly.

Change-Id: I2bd2bf3750c2bd3d672a037edb56f2b0b9bf1379

DirectXMan12/nova-hacking,Brocade-OpenSource/OpenStack-DNRM-Nova,sridevikoushik31/openstack,shahar-stratoscale/nova,DirectXMan12/nova-hacking,blueboxgroup/nova,tianweizhang/nova,CEG-FYP-OpenStack/scheduler,ted-gould/nova,isyippee/nova,virtualopensystems/nova,orbitfp7/nova,sridevikoushik31/nova,jianghuaw/nova,alvarolopez/nova,shail2810/nova,OpenAcademy-OpenStack/nova-scheduler,redhat-openstack/nova,jianghuaw/nova,yrobla/nova,TwinkleChawla/nova,openstack/nova,Yuriy-Leonov/nova,alvarolopez/nova,scripnichenko/nova,openstack/nova,eonpatapon/nova,dstroppa/openstack-smartos-nova-grizzly,raildo/nova,NoBodyCam/TftpPxeBootBareMetal,sridevikoushik31/openstack,berrange/nova,Triv90/Nova,takeshineshiro/nova,whitepages/nova,alexandrucoman/vbox-nova-driver,paulmathews/nova,akash1808/nova,akash1808/nova,mandeepdhami/nova,hanlind/nova,paulmathews/nova,berrange/nova,zaina/nova,badock/nova,varunarya10/nova_test_latest,LoHChina/nova,iuliat/nova,BeyondTheClouds/nova,imsplitbit/nova,cloudbase/nova,ntt-sic/nova,barnsnake351/nova,sebrandon1/nova,alaski/nova,felixma/nova,eayunstack/nova,BeyondTheClouds/nova,qwefi/nova,savi-dev/nova,rahulunair/nova,leilihh/novaha,barnsnake351/nova,klmitch/nova,angdraug/nova,cloudbase/nova-virtualbox,JianyuWang/nova,aristanetworks/arista-ovs-nova,savi-dev/nova,gooddata/openstack-nova,double12gzh/nova,psiwczak/openstack,jeffrey4l/nova,blueboxgroup/nova,bclau/nova,silenceli/nova,noironetworks/nova,qwefi/nova,felixma/nova,luogangyi/bcec-nova,mikalstill/nova,affo/nova,nikesh-mahalka/nova,tealover/nova,mmnelemane/nova,rajalokan/nova,alexandrucoman/vbox-nova-driver,scripnichenko/nova,fnordahl/nova,tanglei528/nova,devendermishrajio/nova_test_latest,Juniper/nova,rickerc/nova_audit,phenoxim/nova,nikesh-mahalka/nova,petrutlucian94/nova,NoBodyCam/TftpPxeBootBareMetal,paulmathews/nova,LoHChina/nova,apporc/nova,JioCloud/nova_test_latest,whitepages/nova,gooddata/openstack-nova,shootstar/novatest,aristanetworks/arista-ovs-nova,maoy/zknova,usc-isi/nova,dawnpower/nova,cloudbau/nova,rajalokan/nova,takeshineshiro/nova,NewpTone/stacklab-nova,mmnelemane/nova,klmitch/nova,eayunstack/nova,maelnor/nova,dims/nova,savi-dev/nova,CiscoSystems/nova,bigswitch/nova,viggates/nova,Tehsmash/nova,josephsuh/extra-specs,tangfeixiong/nova,yrobla/nova,jianghuaw/nova,shail2810/nova,isyippee/nova,ruslanloman/nova,maoy/zknova,cloudbase/nova-virtualbox,jianghuaw/nova,citrix-openstack-build/nova,jeffrey4l/nova,NoBodyCam/TftpPxeBootBareMetal,CloudServer/nova,luogangyi/bcec-nova,watonyweng/nova,devoid/nova,Triv90/Nova,tealover/nova,rahulunair/nova,mahak/nova,houshengbo/nova_vmware_compute_driver,Metaswitch/calico-nova,adelina-t/nova,j-carpentier/nova,bgxavier/nova,akash1808/nova_test_latest,dawnpower/nova,leilihh/novaha,shahar-stratoscale/nova,kimjaejoong/nova,affo/nova,vladikr/nova_drafts,petrutlucian94/nova,ntt-sic/nova,apporc/nova,sridevikoushik31/nova,ruslanloman/nova,projectcalico/calico-nova,mahak/nova,angdraug/nova,zzicewind/nova,spring-week-topos/nova-week,noironetworks/nova,spring-week-topos/nova-week,rickerc/nova_audit,klmitch/nova,maoy/zknova,dstroppa/openstack-smartos-nova-grizzly,Triv90/Nova,usc-isi/extra-specs,usc-isi/extra-specs,NewpTone/stacklab-nova,Stavitsky/nova,edulramirez/nova,kimjaejoong/nova,imsplitbit/nova,leilihh/nova,plumgrid/plumgrid-nova,alaski/nova,eonpatapon/nova,josephsuh/extra-specs,gspilio/nova,Juniper/nova,josephsuh/extra-specs,thomasem/nova,edulramirez/nova,zaina/nova,zhimin711/nova,mahak/nova,Brocade-OpenSource/OpenStack-DNRM-Nova,eharney/nova,sebrandon1/nova,DirectXMan12/nova-hacking,sridevikoushik31/nova,maheshp/novatest,SUSE-Cloud/nova,gooddata/openstack-nova,cloudbau/nova,CCI-MOC/nova,TwinkleChawla/nova,OpenAcademy-OpenStack/nova-scheduler,raildo/nova,fnordahl/nova,Metaswitch/calico-nova,gspilio/nova,rrader/nova-docker-plugin,Francis-Liu/animated-broccoli,dims/nova,fajoy/nova,SUSE-Cloud/nova,citrix-openstack-build/nova,devendermishrajio/nova,cloudbase/nova,openstack/nova,maelnor/nova,vladikr/nova_drafts,orbitfp7/nova,thomasem/nova,JioCloud/nova,belmiromoreira/nova,usc-isi/extra-specs,cyx1231st/nova,CCI-MOC/nova,JioCloud/nova_test_latest,cernops/nova,usc-isi/nova,cloudbase/nova,MountainWei/nova,sileht/deb-openstack-nova,vmturbo/nova,leilihh/nova,CloudServer/nova,psiwczak/openstack,cyx1231st/nova,eneabio/nova,joker946/nova,varunarya10/nova_test_latest,bigswitch/nova,fajoy/nova,belmiromoreira/nova,Francis-Liu/animated-broccoli,tudorvio/nova,tangfeixiong/nova,badock/nova,dstroppa/openstack-smartos-nova-grizzly,phenoxim/nova,vmturbo/nova,sileht/deb-openstack-nova,cernops/nova,mgagne/nova,yosshy/nova,yatinkumbhare/openstack-nova,gooddata/openstack-nova,NeCTAR-RC/nova,devendermishrajio/nova_test_latest,silenceli/nova,yosshy/nova,Tehsmash/nova,bgxavier/nova,ted-gould/nova,CEG-FYP-OpenStack/scheduler,bclau/nova,maheshp/novatest,Yusuke1987/openstack_template,rajalokan/nova,Yusuke1987/openstack_template,eharney/nova,sebrandon1/nova,MountainWei/nova,Juniper/nova,adelina-t/nova,CiscoSystems/nova,eneabio/nova,maheshp/novatest,aristanetworks/arista-ovs-nova,mandeepdhami/nova,houshengbo/nova_vmware_compute_driver,TieWei/nova,zhimin711/nova,sileht/deb-openstack-nova,devoid/nova,hanlind/nova,JioCloud/nova,psiwczak/openstack,BeyondTheClouds/nova,vmturbo/nova,houshengbo/nova_vmware_compute_driver,ewindisch/nova,shootstar/novatest,gspilio/nova,JianyuWang/nova,redhat-openstack/nova,vmturbo/nova,mikalstill/nova,viggates/nova,projectcalico/calico-nova,hanlind/nova,rahulunair/nova,sridevikoushik31/openstack,yrobla/nova,fajoy/nova,zzicewind/nova,petrutlucian94/nova_dev,tudorvio/nova,yatinkumbhare/openstack-nova,ewindisch/nova,rajalokan/nova,tanglei528/nova,cernops/nova,NewpTone/stacklab-nova,petrutlucian94/nova_dev,devendermishrajio/nova,iuliat/nova,j-carpentier/nova,mgagne/nova,sacharya/nova,saleemjaveds/https-github.com-openstack-nova,Yuriy-Leonov/nova,sridevikoushik31/nova,akash1808/nova_test_latest,Stavitsky/nova,sacharya/nova,saleemjaveds/https-github.com-openstack-nova,Juniper/nova,virtualopensystems/nova,plumgrid/plumgrid-nova,TieWei/nova,tianweizhang/nova,double12gzh/nova,klmitch/nova,eneabio/nova,watonyweng/nova,usc-isi/nova,rrader/nova-docker-plugin,mikalstill/nova,joker946/nova,NeCTAR-RC/nova