Fix method/function names case mismatch in core files

Fix method/function names case mismatch in core files

PHP doesn't care much but I think we humans do because we should
call methods by the name we give them. Method fixed are;

- isOk() -> isOK()
- setOk() -> setOK()
- teardown() -> tearDown()

Change-Id: I6b3f0cf3902887058efa426968da380803869e0b