Download some (but not all) kiln repositories using git instead of hg.

Summary:
We've been seeing some flaky behavior on kiln where we can download
the webapp repo using git, but not using hg.  I figure this is a good
time to just move us over to git for everything.  But I'm doing it
slowly, so for now I just move the non-webapp-based repos (Private/* and
Mobile/*), of which there are 12 or 13.

Test Plan:
   % ./update_phabricator_repositories.py -n /var/tmp/
   Adding new repository Mobile-Apps/Group/android: url=ssh://khanacademy.kilnhg.com/Mobile-Apps/Group/android, callsign=GMAA, vcs=git, destdir=/var/tmp/git/Mobile-Apps/Group/android
   Adding new repository Mobile-Apps/Group/hp-touchpad: url=ssh://khanacademy.kilnhg.com/Mobile-Apps/Group/hp-touchpad, callsign=GMAHT, vcs=git, destdir=/var/tmp/git/Mobile-Apps/Group/hp-touchpad
   Adding new repository Mobile-Apps/Group/iPad: url=ssh://khanacademy.kilnhg.com/Mobile-Apps/Group/iPad, callsign=GMAI, vcs=git, destdir=/var/tmp/git/Mobile-Apps/Group/iPad
   Adding new repository Mobile-Apps/Group/iPad-exercises: url=ssh://khanacademy.kilnhg.com/Mobile-Apps/Group/iPad-exercises, callsign=GMAIE, vcs=git, destdir=/var/tmp/git/Mobile-Apps/Group/iPad-exercises
   Adding new repository Mobile-Apps/Group/iPad-old: url=ssh://khanacademy.kilnhg.com/Mobile-Apps/Group/iPad-old, callsign=GMAIO, vcs=git, destdir=/var/tmp/git/Mobile-Apps/Group/iPad-old
   Adding new repository Private/Group/assistly: url=ssh://khanacademy.kilnhg.com/Private/Group/assistly, callsign=GPA, vcs=git, destdir=/var/tmp/git/Private/Group/assistly
   Adding new repository Private/Group/backup-and-analytics: url=ssh://khanacademy.kilnhg.com/Private/Group/backup-and-analytics, callsign=GPBAA, vcs=git, destdir=/var/tmp/git/Private/Group/backup-and-analytics
   Adding new repository Private/Group/office-tools: url=ssh://khanacademy.kilnhg.com/Private/Group/office-tools, callsign=GPOT, vcs=git, destdir=/var/tmp/git/Private/Group/office-tools
   Adding new repository Private/Review/snippets: url=ssh://khanacademy.kilnhg.com/Private/Review/snippets, callsign=GPRS, vcs=git, destdir=/var/tmp/git/Private/Review/snippets
   Adding new repository Private/Review/test: url=ssh://khanacademy.kilnhg.com/Private/Review/test, callsign=GPRT, vcs=git, destdir=/var/tmp/git/Private/Review/test
   Repository https://khanacademy.kilnhg.com/Code/Mobile-Apps/Group/android has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete MAA
   Repository https://khanacademy.kilnhg.com/Code/Mobile-Apps/Group/hp-touchpad has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete MAHT
   Repository https://khanacademy.kilnhg.com/Code/Mobile-Apps/Group/iPad has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete MAI
   Repository https://khanacademy.kilnhg.com/Code/Mobile-Apps/Group/iPad-exercises has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete MAIE
   Repository https://khanacademy.kilnhg.com/Code/Mobile-Apps/Group/iPad-old has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete MAIO
   Repository https://khanacademy.kilnhg.com/Code/Private/Group/assistly has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete PA
   Repository https://khanacademy.kilnhg.com/Code/Private/Group/backup-and-analytics has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete PBAA
   Repository https://khanacademy.kilnhg.com/Code/Private/Group/office-tools has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete POT
   Repository https://khanacademy.kilnhg.com/Code/Private/Group/profanity-tools has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete PPT
   Repository https://khanacademy.kilnhg.com/Code/Private/Review/snippets has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete PRS
   Repository https://khanacademy.kilnhg.com/Code/Private/Review/test has been deleted: run (on toby):
      env PHABRICATOR_ENV=khan ~/internal-webserver/phabricator/bin/repository delete PRT

This is exactly what one would expect.  I then actually ran this
script on toby, and then ran
   ./scripts/repository/test_connection.php GMAHT
to verify that the ssh connection was working properly, and waited a
while and then saw
   % ls /mnt/phabricator/repositories/git/Mobile-Apps/Group/android/
   README
so the repos are actually being fetched successfully.

Reviewers: benkomalo, chris

Reviewed By: chris

Differential Revision: http://phabricator.khanacademy.org/D4155