Dedup flag disabled values

It is possible for TableMerger::DoMerge() to get called multiple times
for the same flat file. Regular resource values handled this but the
flag disabled ones didn't. This makes it so that we handle flag disabled
ones the same as regular.

This also adds to the dump output so that we print the flag name if
there is one.

Fixes: 419314745
Test: Automated
Flag: EXEMPT bugfix
Change-Id: I0f12b7b391fedf691cff689b0d43a55bf0419524