Use MODE_ASK as the default ops mode in Privacy Guard

 * Prompting the user is far more useful as a default behavior. The
   choice will be remembered after the first request.

Change-Id: Ie62f932047f8b761bd0dd9f836bcd1132062edf5
LocationServiceManager: Fix deadlock due to updateMonitoring.

AppOps can be blocked if askOperation is called from main thread.
This causes location service manager to block while updating monitor
information of all location update receivers.

Fix AppOps to report all askOperation calls from main thread.
Also fix location service manager to handle MODE_ASK.

Change-Id: I085f01e992f60456ad24921bf4ce508ece54e8a6
appops: do not prune apps that are not present

Do not prune apps that are not currently present in the device (like sdcards ones). During
booting sdcards are not available but must not be purge from appops, because they are still
present in the android app database.
JIRA: CYAN-2811
Issue: https://jira.cyanogenmod.org/browse/CYAN-2811

Change-Id: I6680cbdf0022812b45d966dffee754399e92accb
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>