Tolerate exceptions while probing for settings that silence alarms

Bug: 32196863

One of the probes checks if the system default alarm ringtone is unset.
On some versions of android this can actually *cause* the system to
attempt to initialize that setting, which in turn fails because the clock
app does not request the WRITE_SETTINGS permission.

Change-Id: I36437e581ce668c786b5d66da0920a5f9da8014f