Handle USER_REMOVED action in DefaultDialerCache

When a user is removed, its entry sticks around in the dialer cache.
This causes a lot of logspam during CTS. This change removes a user from
the default dialer cache when its USER_REMOVED broadcast is sent.

Change-Id: I4c86957fae21e37b213bbf13d26c21df74d85b0a
Fixes: 38161359
Test: manual and unit