onAccountsUpdated shouldn't be called back after listener unregistered

There is a problem of AccountManager that onAccountsUpdated() is
called back even after the OnAccountsUpdatedListener is unregistered.
It may cause application crash.

For example, when rotating a tablet 180 degree with Settings apk
running, com.android.settings.Settings is re-launched 2 times
successively. (Destroy->Create->Destroy->Create)
It repeats adding&removing OnAccountUpdatedListener.

When dialog was being opened in the following cases,
NullPointerException at BackStackRecord.getBreadCrumbTitle()
was happened on 10 inch tablet which has 2 panes on Settings.
* Settings > Language&input > Language
* Settings > Language & input > Text-to-speech output > Speech rate
* Settings > Wi-Fi > Menu > Advanced > Keep Wi-Fi on during sleep
* Settings > Wi-Fi > Menu > Wi-Fi Direct > Rename device

This fix prevents the undesirable callback.

Change-Id: I081f69c90539cca821cf686b4587495135f375e4
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
Before requerying a cursor, check if it is closed.

Before updating a cursor,
it needs to be checked if it is valid.
Currently a defence code only checks
if it is not null.
But in case of "Cursor", it is not valid,
if it is closed.
So just like in CursorAdapter.onContentChanged(),
add the additional defence code to check validation.

Change-Id: I1302f1b6d009897815d4bdb2f20f625688cf9901