Fix memory leak of reactor and reactor_unittest

* Fix memory leak happen in below two cases

Case 1

1. Reactable1 register
2. Reactable2 register
3. Reactable2 unregister during the callback event of Reactable2
4. Reactable1 unregister

In step 3, reactable_removed_ will set to true due to unregister while
reactable->is_executing_ is true, it makes sure we delete Reactable2
after the callback is executed. But it will cause Reactable1 to not be
deleted in step 4.

To avoid this, we can reset reactable_removed_ to false after Reactable
deleted.

Case 2

1. Reactable1 register
2. Reactable2 register
3. Reactable2 unregister during the callback event of Reactable2
4. Reactable1 unregister from different thread during step 3 processing

In step 3, although we reset reactable_removed_ to false after Reactable2
deleted immediately for case 1, if other thread unregister Reactable1
before Reactable2 deleted, Reactable1 will fail to be deleted.

To avoid thie, we add a local variable to check if the Reacable is
executing. If not, deleted the Reactable directly.

* Add unittest for these two cases
* Fix memory leak in reactor_unittest
* Turn on cfi and address flag

Test: sudo ./bluetooth_test_gd
Change-Id: I0a0ca79b439fd3a1bf3ec0fa2b2a43a88e037fbb