Improve MAC address parsing

The Solaris installer requires a MAC address of the form "0:e0:81:5d:c5:31".
Fix virtinst to be handle such zero-compression.

Signed-off-by: John Danielson <john.danielson@sun.com>

diff --git a/virtinst/Guest.py b/virtinst/Guest.py
--- a/virtinst/Guest.py
+++ b/virtinst/Guest.py
@@ -179,7 +179,7 @@ class VirtualNetworkInterface:
 class VirtualNetworkInterface:
     def __init__(self, macaddr = None, type="bridge", bridge = None, network=None):
         if macaddr is not None:
-            form = re.match("^([0-9a-fA-F]{2}:){5}[0-9a-fA-F]{2}$",macaddr)
+            form = re.match("^([0-9a-fA-F]{1,2}:){5}[0-9a-fA-F]{1,2}$",macaddr)
             if form is None:
                 raise ValueError, "Invalid value for MAC address"
         self.macaddr = macaddr