The solution is to open up your most favorite text editor and remove the silly windows LF/CR from the end of each line. Someone borked up - People still use Microsoft? : )

In simple terms ^M is spamming the scripts.

Both of the following files have this issue:

/var/lib/dpkg/info/samba-common.postinst
/var/lib/dpkg/info/samba-common.postrm

Once you remove the ^M from the end of every line, it will both install and remove correctly. It's quite probable that the other samba-common files in this directory are also having the same problem - though I didn't check.