Fix missing service call when rebinding to VrCore

When rebinding to VrCore after a VrCore crash we weren't calling
onCurrentVrActivityChanged().

Bug: b/69839187

Test: Went through the repro steps in b/69839187 and confirmed we
successfully recover after VrCore dies and is rebound.

Change-Id: Idbd7acb438e8b7754743c5ccaaa68b4e0a686d33
(cherry picked from commit d03fa742c2f29330d138ba6e2241f13eb527b9b5)