Move generated aidl/logtags java classes to a subfolder

So that they can't be generated into src/, which would be added to the
source list automatically.

Bug: 36698184
Test: m telephony-common without this change, pass
Test: m telephony-common without the cleanspec, fail with dup class
Test: m telephony-common with the cleanspec, pass
Change-Id: I7b2fc1847d52ff4a9ba8c69e76123fe152629ef8