Adds tty password entry for neutronclient

Added functionality from keystoneclient to fallback to the tty for password
entry if no password is given via the environment or the --os-password option.

Closes-Bug: 1356550

Change-Id: I7d0428a8901cae667ef598aa515e108a3a679540
Merge "Adds tty password entry for neutronclient"