qemuargv2xmltest: Resurrect RBD and iSCSI auth

qemuargv2xmltest: Resurrect RBD and iSCSI auth

Ressurect the disk-drive-network-iscsi-auth and disk-drive-network-rbd-auth
tests.  Make adjustments to the args and xml file to be compatible with
other changes made to the non "-auth" so that the only difference is the
authentication information.

Adjust the qemuargv2xmltest.c to filter out "<secret" and "</auth>" since
the args -> xml has no concept of usage it doesn't get printed. This results
in the </auth> being printed on the same line as "<secret" and the secret
XML is not closed - a bit of an issue, but soon to be fixed.