Fix to disallow server name with all blank spaces

* Nova CLI allows server name to be created with all blank characters.
  This fix will disallow a server name with all blank spaces during
  server/instance creation as well as while updating/renaming a server
* Adding unit tests to test the above scenarios (create & rename
  server with blank spaces)

Fixes bug 1175956

Change-Id: I58af207c4a6b8579bb172d4bb612e0aa2aa6b498
Merge "Fix to disallow server name with all blank spaces"