Sync rootwrap with code from oslo

The rootwrap module had been directly edited in commit 1d366293.
These are all minor changes bringing neutron up to commit c03f247

c03f247 Skip hidden files while traversion rootwrap filters
3f4d1d5 Fix os.getlogin() problem with no tty
fc04531 Send rootwrap exit error message to stderr
3663010 rootwrap: improve Python 3 compatibility
28395d9 Fixes files with wrong bitmode

Fixes bug #1229492

Change-Id: Ica406e021700578b27c3337498011059c3a78719
Merge "Sync rootwrap with code from oslo"