Remove unused gitdb dependency
Remove unused gitdb dependency

Newer versions of gitdb are conflicting with the dependencies of newer
versions of GitPython, so they can not be properly coinstalled

This dep was introduced in If069ebb33ee4cb7f81308c68849ba9f969752d25
but not actually used back then. drop it.

Change-Id: Idc30b635dcba04aec47a3537cb9cc490eb255da9

openstack/tripleo-common,openstack/tripleo-common