Add pbr to installation requirements

Add pbr to the list of installation requirements so that it is installed
via pip before this library is installed, instead of with easy_install.
This avoids issues like Bug #1384919, and ensures that projects that use
this library as a dependency are properly installed.

Change-Id: I6c155370dbd01fe4748d5137bdf288e8d3e1a67e
Add get_my_ip()

At the moment function _get_my_ip() exists (at least) in Cinder,
Ironic, Neutron, Nova and Tuskar, so there is a sense to keep
it in common code.

Change-Id: I3c37d6ea3e8bef7b8a5e21baedd1b2b94369515f
Merge "Add get_my_ip()"
Merge "Add pbr to installation requirements"