Handle condition changes when metric is not active.

Treat metric activation like conditions as much as possible. Keep track
of condition changes even when metric is not active. Right now, we
ignore all condition changes if metric is not active.

This is a band-aid fix. Ideally, we should re-think how metric activation is
implemented and consider implementing it as a condition with a timebomb.

Bug: 130838341
Test: statsd_test
Test: cts-tradefed run cts-dev -m CtsStatsdHostTestCases -t
android.cts.statsd.metric

Change-Id: I96bb7a7c6ee88359f310065e166f858be945eaff