Add ssh_private_keys default to common
Add ssh_private_keys default to common

Without an empty default the run will fail if ssh_private_keys is not
defined.

sivakom/ursula,kennjason/ursula,aldevigi/ursula,rongzhus/ursula,paulczar/ursula,fancyhe/ursula,lihkin213/ursula,narengan/ursula,masteinhauser/ursula,j2sol/ursula,fancyhe/ursula,channus/ursula,pgraziano/ursula,ddaskal/ursula,narengan/ursula,persistent-ursula/ursula,wupeiran/ursula,mjbrewer/ursula,nirajdp76/ursula,allomov/ursula,mjbrewer/ursula,allomov/ursula,persistent-ursula/ursula,dlundquist/ursula,channus/ursula,msambol/ursula,panxia6679/ursula,twaldrop/ursula,edtubillara/ursula,nirajdp76/ursula,davidcusatis/ursula,nirajdp76/ursula,wupeiran/ursula,MaheshIBM/ursula,wupeiran/ursula,knandya/ursula,pbannister/ursula,mjbrewer/ursula,ddaskal/ursula,blueboxgroup/ursula,pgraziano/ursula,andrewrothstein/ursula,knandya/ursula,narengan/ursula,EricCrosson/ursula,rongzhus/ursula,panxia6679/ursula,greghaynes/ursula,rongzhus/ursula,zrs233/ursula,lihkin213/ursula,ddaskal/ursula,dlundquist/ursula,twaldrop/ursula,MaheshIBM/ursula,aldevigi/ursula,j2sol/ursula,pbannister/ursula,jwaibel/ursula,blueboxgroup/ursula,msambol/ursula,knandya/ursula,kennjason/ursula,pgraziano/ursula,msambol/ursula,knandya/ursula,channus/ursula,zrs233/ursula,edtubillara/ursula,kennjason/ursula,sivakom/ursula,davidcusatis/ursula,sivakom/ursula,andrewrothstein/ursula,fancyhe/ursula,davidcusatis/ursula,twaldrop/ursula,masteinhauser/ursula,pgraziano/ursula,ryshah/ursula,twaldrop/ursula,lihkin213/ursula,andrewrothstein/ursula,nirajdp76/ursula,edtubillara/ursula,masteinhauser/ursula,greghaynes/ursula,persistent-ursula/ursula,wupeiran/ursula,aldevigi/ursula,persistent-ursula/ursula,j2sol/ursula,zrs233/ursula,pbannister/ursula,blueboxgroup/ursula,greghaynes/ursula,narengan/ursula,allomov/ursula,panxia6679/ursula,zrs233/ursula,j2sol/ursula,dlundquist/ursula,paulczar/ursula,EricCrosson/ursula,masteinhauser/ursula,panxia6679/ursula,ryshah/ursula,MaheshIBM/ursula,lihkin213/ursula,ddaskal/ursula,ryshah/ursula,EricCrosson/ursula,ryshah/ursula,channus/ursula,rongzhus/ursula,paulczar/ursula,fancyhe/ursula,blueboxgroup/ursula,jwaibel/ursula,edtubillara/ursula,jwaibel/ursula