Don't drop max_session_age column in transaction during upgrade

It depends on what version of schema we are upgrading from as to
whether or not this column exists in the system_config table.  If
the database is relatively new and was created from a schema which
does not define this column, it won't have it, and the upgrade would
abort with an error.  Therefore we need to process this outside of
the transaction block, allowing it to fail and continue.

Change-Id: I7e625a2d5269eb76e64901c2302a661135bd9021
Signed-off-by: Shawn O. Pearce <sop@google.com>
2 files changed