Add ability to filter on flavor name

Rackspace have recently added 'Performance' flavors. These flavors
distinguish themselves from other flavors only by a difference in
their name. The current config can only filter by RAM. Add a config
option for indicating a string that should be found in the flavor name.

Change-Id: I42448dde02f405182e887bf928b152cf97d2a0cb
Merge "Add ability to filter on flavor name"