PDO MySQL's getCode() didn't match errorInfo

Summary: Fixes #3206

Closes https://github.com/facebook/hhvm/pull/3246

Reviewed By: joelm, fredemmott, ptarjan

Differential Revision: D1447243

Pulled By: svcscm
Catch FailedToListenException from hhprof server startup

Summary: This is probably the source of the uncaught FailedToListenException
that's causing sandbox mode to crash---it's the only call to
Server::start() I can see that's not wrapped in a try-catch.

Reviewed By: @jdelong

Differential Revision: D1465343