iotests: Add 'check -ssh' option to test Secure Shell block device.

Note in order to run these tests on ssh, you must be running a local
ssh daemon, and that daemon must accept loopback connections, and
ssh-agent has to be set up to allow logins on the local daemon.  In
other words, the following command should just work without demanding
any passphrase:

 ssh localhost
Signed-off-by: NRichard W.M. Jones <rjones@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

tests/qemu-iotests/common

@@ -137,6 +137,7 @@ check options
     -rbd                test rbd
     -sheepdog           test sheepdog
     -nbd                test nbd
+    -ssh                test ssh
     -xdiff		graphical mode diff
     -nocache		use O_DIRECT on backing file
     -misalign		misalign memory allocations
@@ -206,6 +207,10 @@ testlist options
 	    IMGPROTO=nbd
 	    xpand=false
 	    ;;
+        -ssh)
+            IMGPROTO=ssh
+            xpand=false
+            ;;
 	-nocache)
 	    QEMU_IO_OPTIONS="$QEMU_IO_OPTIONS --nocache"
 	    xpand=false

tests/qemu-iotests/common.rc

@@ -52,6 +52,9 @@ if [ "$IMGPROTO" = "file" ]; then
 elif [ "$IMGPROTO" = "nbd" ]; then
     TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
     TEST_IMG="nbd:127.0.0.1:10810"
+elif [ "$IMGPROTO" = "ssh" ]; then
+    TEST_IMG_FILE=$TEST_DIR/t.$IMGFMT
+    TEST_IMG="ssh://127.0.0.1$TEST_IMG_FILE"
 else
     TEST_IMG=$IMGPROTO:$TEST_DIR/t.$IMGFMT
 fi