Fix RunLinuxCmd for Debian
Fix RunLinuxCmd for Debian

Verified against Debian 7,8, and 9

iamshital/azure-linux-automation,iamshital/azure-linux-automation,konkasoftci/azure-linux-automation,v-sirebb/azure-linux-automation,Nidylei/azure-linux-automation,v-sirebb/azure-linux-automation,Nidylei/azure-linux-automation,konkasoftci/azure-linux-automation,hglkrijger/azure-linux-automation,konkasoftci/azure-linux-automation,iamshital/azure-linux-automation,hglkrijger/azure-linux-automation,Nidylei/azure-linux-automation,hglkrijger/azure-linux-automation,v-sirebb/azure-linux-automation