Update provisioning sha1 computation to handle multiple common folders

The current computation of provisioningScriptSha1 computation is based on an assumption of a single common folder. This needs to be changed so that 

1) Provisioning script change in macos, linux or windows folder should cause a  change in tier2 sha1 of the dependent platform, only (change in windows common folder should not effect the linux/macos script sha1 and so on)

2) Provisioning script change in Unix folder should cause a change in tier2 sha1 of Linux/MacOS 
3) File change in shared folder should trigger full tier2 rebuild