Don't hold mDataEnabledSettings lock if not needed.

Since most public APIs in mDataEnabledSettings are synchronized
methods, we don't need to lock mDataEnabledSettings explicitly.
We also shouldn't lock it when no longer needed, which could lead
to deadlock.

Bug: 71517029
Test: regression test
Change-Id: I0f3f51af94e48b4d31f703f444102f53fd466758