core: Cleanup OpenStackImageProviderProxy

Remove unused methods.

Change-Id: I675fb052b310746dceee0314d7ec2201386ed664
Signed-off-by: Allon Mureinik <amureini@redhat.com>
core: rm unused SessionDataContainer.containsKey

Change-Id: I9ab7dee562e32657983c11b41189aee884f2880e
Signed-off-by: Allon Mureinik <amureini@redhat.com>