Allow committing allowing state loss on detached FragmentManager.

Bug 36702993

Instead of throwing an exception during commitAllowStateLoss()
or commitNowAllowingStateLoss(), silently drop the transaction
when the FragmentManager is detached.

Test: ran fragment tests
Change-Id: Ic1f36c9fdbaa598b17180cfa6afbf8fa45a952a4
2 files changed