Typo in CameraParameters::set

Change-Id: I05a6a6adb02c326ae406be24471bd7290c481b5b
Typo: 'key' --> 'value'
camera: Fix the heap corruption issue

 * Add locking around flatten/unflatten because they alter mMap and
   all hope and sleep is lost if it changes while we're iterating.
 * It's even worse if the memory backing the params string changes
   underneath of us :(

Change-Id: I06d85343a4a1c0143fab0687fda9e1d95a28440e