Change the min/max q validation in lossless mode

This commit changed how q is validated in lossless mode. With this
commit, when --lossless=1 is specificed at commandline, --min-q and
--max-q are now ignored. This is to make the option non-ambiguious.

Change-Id: I33e85690460537509d33be75d6a3597be4affc09