as lp:494185 points out, need better logic for selecting ec2 mirror

Over all, it takes a much better "hit" to select a ec2 mirror. This
should greatly reduce the chance for false positives.

The chance for error is then:
a.) availability zone names change form (ie, no longer '<region>[a-z]')
b.) there are images in a new region before a mirror is up, but the
    dns entry already exists
c.) availability zone empty or failed

I think its reasonably good, the only thing that concerns me is the
possibility of getaddrinfo hanging.

=== modified file 'debian/changelog'
--- debian/changelog	2009-10-26 16:18:06 +0000
+++ debian/changelog	2009-12-11 20:13:11 +0000
@@ -1,3 +1,9 @@
+ec2-init (0.4.999-0ubuntu8) karmic; urgency=low
+
+  * fix mirror selection for us-west-1 (LP: #494185)
+
+ -- Scott Moser <smoser@ubuntu.com>  Fri, 11 Dec 2009 15:12:19 -0500
+
 ec2-init (0.4.999-0ubuntu7) karmic; urgency=low
 
   * work around differences in eucalyptus ephemeral mounts (LP: #458850)

=== modified file 'debian/rules'
--- debian/rules	2009-09-25 14:17:17 +0000
+++ debian/rules	2009-12-11 20:16:50 +0000
@@ -3,6 +3,7 @@
 DEB_PYTHON_SYSTEM=pycentral
 include /usr/share/cdbs/1/class/python-distutils.mk
 include /usr/share/cdbs/1/rules/debhelper.mk
+include /usr/share/cdbs/1/rules/simple-patchsys.mk
 DEB_DH_INSTALLINIT_ARGS=-o
 
 DEB_UPDATE_RCD_PARAMS:= start 15 2 3 4 5 . stop 20 1 .

=== modified file 'ec2init/__init__.py'
--- ec2init/__init__.py	2009-08-26 01:23:52 +0000
+++ ec2init/__init__.py	2009-12-11 20:12:11 +0000
@@ -88,12 +88,13 @@
         return hostname
 
     def get_mirror_from_availability_zone(self, availability_zone):
-        if availability_zone.startswith("us"):
-            return 'http://us.ec2.archive.ubuntu.com/ubuntu/'
-        elif availability_zone.startswith("eu"):
-            return 'http://eu.ec2.archive.ubuntu.com/ubuntu/'
-
-        return 'http://archive.ubuntu.com/ubuntu/'
+        # availability is like 'us-west-1b' or 'eu-west-1a'
+        try:
+            host="%s.ec2.archive.ubuntu.com" % availability_zone[:-1]
+            socket.getaddrinfo(host, None, 0, socket.SOCK_STREAM)
+            return 'http://%s/ubuntu/' % host
+        except:
+            return 'http://archive.ubuntu.com/ubuntu/'
 
     def wait_for_metadata_service(self):
         timeout = 2