iotests: Add test for driver=qcow2, format=qcow2

While specifying a different driver and format is obviously invalid,
specifying the same driver once through driver and once through format
is invalid as well. Add a test for it.
Signed-off-by: NMax Reitz <mreitz@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-id: 1423162705-32065-5-git-send-email-mreitz@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

tests/qemu-iotests/051

@@ -93,6 +93,7 @@ echo
 run_qemu -drive file="$TEST_IMG",format=foo
 run_qemu -drive file="$TEST_IMG",driver=foo
 run_qemu -drive file="$TEST_IMG",driver=raw,format=qcow2
+run_qemu -drive file="$TEST_IMG",driver=qcow2,format=qcow2
 
 echo
 echo === Overriding backing file ===

tests/qemu-iotests/051.out

@@ -43,6 +43,9 @@ QEMU_PROG: -drive file=TEST_DIR/t.qcow2,driver=foo: could not open disk image TE
 Testing: -drive file=TEST_DIR/t.qcow2,driver=raw,format=qcow2
 QEMU_PROG: -drive file=TEST_DIR/t.qcow2,driver=raw,format=qcow2: could not open disk image TEST_DIR/t.qcow2: Driver specified twice
 
+Testing: -drive file=TEST_DIR/t.qcow2,driver=qcow2,format=qcow2
+QEMU_PROG: -drive file=TEST_DIR/t.qcow2,driver=qcow2,format=qcow2: could not open disk image TEST_DIR/t.qcow2: Driver specified twice
+
 
 === Overriding backing file ===