Remove Settings from recents after app uninstall

SettingsActivity now calls finishAndRemoveTask
instead of only finish() to prevent blank
recent task from showing in overview.

Test: Visually inspected bug doesn't exist. Wrote
Roboelectric tests

Fixes: 129733119

Change-Id: I5b73c1b611e6eb52bb6665c215276efdc85c19b2