Handle deleted timers gracefully

Bug: 26591272

Prior to dazzle, timers could inhabit a state of "DELETED" (value = 5).
In dazzle and beyond there is no reason to preserve such a state, but
it is possible for timers to exist in SharedPreferences in such a state,
so it must be handled gracefully.

Change-Id: I1754ef898dfff84c0a3e807c4bd0dd1473f87aad