Remove a load of identical definitions of set_difference

Signed-off-by: John Else <john.else@citrix.com>
Remove unused function for handling RHEL3

This function hasn't been used since Oxford, and we haven't supported
RHEL 3 for a while.

Signed-off-by: John Else <john.else@citrix.com>
Fix typos

Signed-off-by: John Else <john.else@citrix.com>
Remove redundant import code

These files aren't being compiled.

Signed-off-by: John Else <john.else@citrix.com>
Fix comment

Signed-off-by: John Else <john.else@citrix.com>