Print human-readable OEM managed states

For NetworkTemplate and NetworkIdentity, print human-readable
representations of the OEM managed state in the classes' respective
toString() functions.

Bug: 180557699
Test: Manual - run atest NetworkTemplateTest NetworkIdentityTest
and verify that the logcat output shows the String representation of the
OEM managed state correctly.

Change-Id: Ia180b911f91f41937ac713e6b3691d82f682e146