Ignore toast request of pinning if request interval is too short

Symptom:
System crash happens if an application repeatedly requests to finish
itself in pinning state.

Root cause:
Toast for pinning state is shown when the application requests to
finish itself. Every toasts use file descripters and they consumes all
available file descripters. System crash happens because of file
descriptor shortage.

Solution:
Ignore toast request for pinning state if request interval is too short.

Bug: 34211454

Change-Id: I4c3b45825270ab96fcfb24723195e9189709c2ec