Fix preference puts with "null" values.

Null values were being written out as <null /> elements in the
XML prefs file (as expected). This allowed the getFoo() functions
to work correctly because they treated null values as missing mappings
but containsKey would fail.

bug: https://code.google.com/p/android/issues/detail?id=64563
Change-Id: I1f466d01db96bf26e208d4fed3a6f257228bea5d
MountService listeners can not be unregistered

When unregistering MountService listeners, their Binder proxy
objects were compared to registered listeners instead of their
backing objects.

Change-Id: Ie98a686b1d17544f1eda59fb3eb0dc02d836c1b2
Add NULL check in updateProxyConfig

If the exclusionList was null in updateProxyConfig the VM would
crash when converting it to a UTF8 string. Avoid this by adding a
null check.

Change-Id: I0d8106fd54385bd9ae9c652a6c67d459a119cf2b
Merge "Add NULL check in updateProxyConfig" into kitkat
Merge "MountService listeners can not be unregistered" into kitkat
Merge "Fix preference puts with "null" values." into kitkat