Extend virt-install timeout on aarch64

I think aarch64 desktop images are often failing to build because
it takes longer than the timeout, so let's bump it a bit.

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

createhdds.py

@@ -294,9 +294,14 @@ class VirtInstallImage(object):
         arch = self.arch
         fedoradir = 'fedora/linux'
         memsize = '3072'
+        timeout = 3600
         if arch == "ppc64le":
             fedoradir = 'fedora-secondary'
             memsize = '4096'
+        if arch == "aarch64":
+            # desktop images take quite a while to build on aarch64,
+            # particularly on the slower worker on stg
+            timeout = 7200
 
         variant = self.variant
         # From F31 onwards, Workstation tree is not installable and we
@@ -347,7 +352,7 @@ class VirtInstallImage(object):
                 logger.debug("Command: %s", ' '.join(args))
                 if not textinst:
                     logger.info("Connect via VNC to monitor")
-                ret = subprocess.call(args, timeout=3600)
+                ret = subprocess.call(args, timeout=timeout)
             except subprocess.TimeoutExpired:
                 logger.warning("Image creation timed out!")
                 # clean up the domain again