Replace BareMetalDriver with IronicDriver in option help string
Replace BareMetalDriver with IronicDriver in option help string

baremetal.BareMetalDriver is gone, the help should say
ironic.IronicDriver.

Change-Id: I2398bcd05ea46349f196981d8cca5c405984da4a
Stavitsky/nova,belmiromoreira/nova,devendermishrajio/nova_test_latest,varunarya10/nova_test_latest,felixma/nova,MountainWei/nova,hanlind/nova,mahak/nova,adelina-t/nova,blueboxgroup/nova,BeyondTheClouds/nova,phenoxim/nova,klmitch/nova,yatinkumbhare/openstack-nova,klmitch/nova,jeffrey4l/nova,devendermishrajio/nova,watonyweng/nova,JioCloud/nova,hanlind/nova,jianghuaw/nova,cernops/nova,kimjaejoong/nova,zhimin711/nova,Juniper/nova,TwinkleChawla/nova,bgxavier/nova,edulramirez/nova,double12gzh/nova,vmturbo/nova,raildo/nova,Tehsmash/nova,vmturbo/nova,BeyondTheClouds/nova,CEG-FYP-OpenStack/scheduler,cloudbase/nova,petrutlucian94/nova,bigswitch/nova,kimjaejoong/nova,hanlind/nova,alaski/nova,openstack/nova,ted-gould/nova,yosshy/nova,MountainWei/nova,yosshy/nova,j-carpentier/nova,sebrandon1/nova,zzicewind/nova,felixma/nova,joker946/nova,joker946/nova,Juniper/nova,zaina/nova,mandeepdhami/nova,noironetworks/nova,jianghuaw/nova,gooddata/openstack-nova,isyippee/nova,blueboxgroup/nova,apporc/nova,belmiromoreira/nova,whitepages/nova,scripnichenko/nova,shail2810/nova,cernops/nova,CloudServer/nova,Juniper/nova,Francis-Liu/animated-broccoli,mahak/nova,akash1808/nova_test_latest,klmitch/nova,watonyweng/nova,edulramirez/nova,LoHChina/nova,TwinkleChawla/nova,adelina-t/nova,gooddata/openstack-nova,barnsnake351/nova,whitepages/nova,rahulunair/nova,iuliat/nova,rajalokan/nova,CloudServer/nova,jianghuaw/nova,fnordahl/nova,noironetworks/nova,thomasem/nova,sebrandon1/nova,gooddata/openstack-nova,eonpatapon/nova,shail2810/nova,JioCloud/nova_test_latest,Francis-Liu/animated-broccoli,nikesh-mahalka/nova,mikalstill/nova,CEG-FYP-OpenStack/scheduler,akash1808/nova,akash1808/nova_test_latest,tangfeixiong/nova,LoHChina/nova,JioCloud/nova,apporc/nova,j-carpentier/nova,NeCTAR-RC/nova,mmnelemane/nova,cernops/nova,alaski/nova,thomasem/nova,nikesh-mahalka/nova,devendermishrajio/nova,mandeepdhami/nova,scripnichenko/nova,mahak/nova,dims/nova,klmitch/nova,openstack/nova,tealover/nova,ruslanloman/nova,raildo/nova,JianyuWang/nova,Juniper/nova,devendermishrajio/nova_test_latest,vmturbo/nova,BeyondTheClouds/nova,petrutlucian94/nova,akash1808/nova,barnsnake351/nova,cyx1231st/nova,rahulunair/nova,phenoxim/nova,rahulunair/nova,zaina/nova,isyippee/nova,gooddata/openstack-nova,zhimin711/nova,mikalstill/nova,jeffrey4l/nova,openstack/nova,takeshineshiro/nova,eonpatapon/nova,alvarolopez/nova,tudorvio/nova,bgxavier/nova,takeshineshiro/nova,mmnelemane/nova,bigswitch/nova,tangfeixiong/nova,rajalokan/nova,sebrandon1/nova,alvarolopez/nova,fnordahl/nova,ted-gould/nova,JianyuWang/nova,mikalstill/nova,rajalokan/nova,NeCTAR-RC/nova,iuliat/nova,CCI-MOC/nova,ruslanloman/nova,yatinkumbhare/openstack-nova,tealover/nova,vmturbo/nova,cyx1231st/nova,CCI-MOC/nova,varunarya10/nova_test_latest,jianghuaw/nova,cloudbase/nova,rajalokan/nova,zzicewind/nova,Stavitsky/nova,dims/nova,tudorvio/nova,cloudbase/nova,Tehsmash/nova,JioCloud/nova_test_latest,double12gzh/nova