Don't clean generated java sources when AIDL list changes

AIDL doesn't generate into the intermediate src directory, we pass exact
aidl->java files to the compiler. So there is no need to clean the
intermediate src directory when the aidl file list changes for a module.

Test: None, just code inspection
Change-Id: I01feff7cc399ac5b88b83333a1ac86928d0a81e6