Workaround RHBZ #1439388 for F26 (with an updates.img)

This bug is causing havoc with image creation on openqa01, so
use an updates.img for F26 image builds until it's fixed.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

createhdds.py

@@ -244,9 +244,12 @@ class VirtInstallImage(object):
             arch = self.arch
             if arch == 'i686':
                 arch = 'i386'
+            xargs = "inst.ks=file:/{0}.ks".format(self.name)
+            if self.release == 26:
+                # workaround RHBZ #1439388: remove when fixed in F26
+                xargs += " inst.updates=https://www.happyassassin.net/updates/1439388.img"
             args = ["virt-install", "--disk", "size={0},path={1}".format(self.size, tmpfile),
-                    "--os-variant", shortid, "-x",
-                    "inst.ks=file:/{0}.ks".format(self.name), "--initrd-inject",
+                    "--os-variant", shortid, "-x", xargs, "--initrd-inject",
                     "{0}/{1}.ks".format(SCRIPTDIR, self.name), "--location",
                     loctmp.format(str(self.release), self.variant, arch), "--name", "createhdds",
                     "--memory", "2048", "--noreboot", "--wait", "-1"]