Change old name of NamespaceManager class to the new name: InstanceManager.
The change was introduced in commit cb4911d and the name was not changed
everywhere.

Change-Id: Icf1fda9922ffc7d21cde7ee206d9e14c8ca31204
Merge "Change old name of NamespaceManager class to the new name: InstanceManager. The change was introduced in commit cb4911d and the name was not changed everywhere."