Camera NDK: fix deadlock issues

1. Fix AMessage contains last reference to session
   issue
2. Fix disconnectLocked waits on dead session issue

Test: add some sleeps to make deadlock scenarios pops in CTS
      and then run CTS 100 times.
Bug: 67965633

Change-Id: If0ab9e33de12969dcb5f1d10e96f47f13024f399