Prevent network depersonalization dialog from showing multiple instances.

The EVENT_SIM_NETWORK_LOCKED event in Telephony triggers displaying the
depersonalization dialog.  It appears, however, that there are instances
when the EVENT_SIM_NETWORK_LOCKED event gets triggered multiple times,
resulting in multiple stacked dialogs being shown.

Added singleton code into the dialog to ensure only a single instance can
be opened at the same time.

Bug: 22963631
Change-Id: Ib43b34acdc9da7dcf4b1cfc4c37ba30b10d16cad
2 files changed