neutronclient shows low-level logs in console screen

Neutron command lines always display some useless information. This
should be avoided. This commit modifies the default level of console
stream to WARNING.

Closes-bug: #1356735

Change-Id: I997dad9ce3fc3eb795e4e44b27d211fa619c1907
Merge "neutronclient shows low-level logs in console screen"