diskbackend: Set relative path for media change

Via the virt-manager UI we aren't converting relative path to
absolute path, even though we do it internally when needed.

We were benefiting from this in the test suite in some ways, so we
need to adjust tests to strip out the dev dir on XML comparison

Signed-off-by: Cole Robinson <crobinso@redhat.com>

tests/uitests/test_mediachange.py

@@ -1,6 +1,9 @@
 # This work is licensed under the GNU GPLv2 or later.
 # See the COPYING file in the top-level directory.
 
+import os
+
+import tests
 from . import lib
 
 
@@ -10,6 +13,7 @@ from . import lib
 
 def testMediaChange(app):
     vmname = "test-many-devices"
+    app.uri = tests.utils.URIs.test_remote
     app.open(show_console=vmname)
     win = app.find_details_window(vmname,
             click_details=True, shutdown=True)
@@ -39,7 +43,7 @@ def testMediaChange(app):
         entry.text == "Floppy_install_label (/dev/fdb)")
 
     # Specify manual path
-    path = "/tmp/aaaaaaaaaaaaaaaaaaaaaaa.img"
+    path = "/pool-dir/UPPER"
     entry.set_text(path)
     appl.click()
     lib.utils.check(lambda: not appl.sensitive)
@@ -88,10 +92,16 @@ def testMediaHotplug(app):
     entry = win.find("media-entry")
     appl = win.find("config-apply")
 
-    # CDROM + physical
     hw.find("IDE CDROM 1", "table cell").click()
     lib.utils.check(lambda: not entry.text)
-    entry.set_text("/dev/sr0")
+    # Catch path does not exist error
+    entry.set_text("/dev/sr7")
+    appl.click()
+    app.click_alert_button("non-existent path '/dev/sr7", "Close")
+
+    # Check relative path while we are at it
+    path = "virt-install"
+    entry.set_text(path)
     appl.click()
     app.click_alert_button("changes will take effect", "OK")
     lib.utils.check(lambda: not appl.sensitive)
@@ -101,4 +111,4 @@ def testMediaHotplug(app):
     win.find("Shut Down", "push button").click()
     run = win.find("Run", "push button")
     lib.utils.check(lambda: run.sensitive)
-    lib.utils.check(lambda: entry.text == "Fedora12_media (/dev/sr0)")
+    lib.utils.check(lambda: entry.text == os.path.abspath(path))