Persist metric activation across beta4/5 ota

In beta 4, activeEventActivation proto object does not have a state
field and assumed to be active if it is written to disk. In beta 5, we
add a state field to support persisting metric activation status across
a system server crash. However, if a device updated from beta 4 to 5, we
don't have any knowledge of the state when we read. Therefore, assume
the lack of the state field as the event activation should be active for
the provided ttl.

Bug: 134795027
Test: used flashstation to flash a device to beta 4. Then manually push
and activate a simple config. Then use vendor/google/tools/flashall to
update to qt-dev + this change. Manually ensure metric/config are still
active.
Test: gts-tradefed run gts-dev --module GtsStatsdHostTestCases
Test: bit statsd_test:*

Change-Id: I8594d04efaa2ae1f669113aaffd33e5fa5851e73