Fixed problems w/ 2nd repo init if first repo init had bad URL.

This is the simplest fix: if we had problems syncing the
manifest.git directory and we were the ones that created it,
we should delete it.  This doesn't try to do anything complex
like try to recover from a .repo directory that got broken in
some other way.

This is filed as: <http://crosbug.com/13403>

TEST=manual

Init once with a bad URL:
  $ repo init -u http://foobar.example.com
  Getting manifest ...
     from http://foobar.example.com
  Connection closed by 172.22.121.77
  error: Couldn't resolve host 'foobar.example.com' while accessing http://foobar.example.com/info/refs

  fatal: HTTP request failed
  fatal: cannot obtain manifest http://foobar.example.com

Init again: identical to the first.  Good:
  $ repo init -u http://foobar.example.com
  Getting manifest ...
     from http://foobar.example.com
  Connection closed by 172.22.121.77
  error: Couldn't resolve host 'foobar.example.com' while accessing http://foobar.example.com/info/refs

  fatal: HTTP request failed
  fatal: cannot obtain manifest http://foobar.example.com

Init with correct URL:
  $ repo init -u http://git.chromium.org/git/manifest -m minilayout.xml
  Getting manifest ...
     from http://git.chromium.org/git/manifest
  [ ... cut ... ]

  repo initialized in /.../repoiniterr

Try a bad URL after a good one; it doesn't get saved (good):
  $ repo init -u http://foobar.example.com
  Connection closed by 172.22.121.77
  error: Couldn't resolve host 'foobar.example.com' while accessing http://foobar.example.com/info/refs

  fatal: HTTP request failed
  fatal: cannot obtain manifest http://foobar.example.com

Just to confirm, I can still do a good one after a bad...
  $ repo init -u http://git.chromium.org/git/manifest -m minilayout.xml

  Your Name  [George Washington]:
  Your Email [george@washington.example.com]:

  Your identity is: George Washington <george@washington.example.com>
  is this correct [y/n]? y

  repo initialized in /.../repoiniterr

Change-Id: I1692821a330d97b1d218b2e191a93245b33f2362

subcmds/init.py

@@ -14,6 +14,7 @@
 # limitations under the License.
 
 import os
+import shutil
 import sys
 
 from color import Coloring
@@ -137,6 +138,11 @@ to update the working directory files.
     if not m.Sync_NetworkHalf():
       r = m.GetRemote(m.remote.name)
       print >>sys.stderr, 'fatal: cannot obtain manifest %s' % r.url
+
+      # Better delete the manifest git dir if we created it; otherwise next
+      # time (when user fixes problems) we won't go through the "is_new" logic.
+      if is_new:
+        shutil.rmtree(m.gitdir)
       sys.exit(1)
 
     syncbuf = SyncBuffer(m.config)