alembic: script modifications due to errors

alembic: script modifications due to errors

A couple of the scripts had errors that would not allow a full migration to
take place.  The extensions table needed to make its 'id' column a primary
key in order to work with mysql.  The other script ...add_endpoints... was
missing tables that it was trying to add columns to.

Added the primary key on id for extensions and added the tables in for the
missing pjsip configuration options.  While it is not ideal to modify already
released scripts this was a case where it had to be done due to errors in
the script and lacking a better alternative.

Review: https://reviewboard.asterisk.org/r/3167/

git-svn-id: https://origsvn.digium.com/svn/asterisk/branches/12@407019 65c4cc65-6c06-0410-ace0-fbb531ad65f3