Camera2: fix FC when switching camera in video mode

mFocusManager's manager needs to be updated before startPreview,
otherwise setParameters will be called with an invalid preview
mode resulting in a crash on some device (in this case, aries).

Change-Id: I32c113e744f95b4939c070b3aad8b4b5c53fce65
Merge branch 'cm-11.0' into martincz