Correctly set oat class status after initializing

The previous CL had a bug where it would not set the oat class status
for initialized classes that had run the class initializer for the
boot image case.

Aims to fix random dex2oat crashes during boot image creation.

Bug: 62402160
Test: test-art-host

Change-Id: Ia1814fc91ec71c9556eb37699a63be3b09ff6188