Set pool_recycle to deal with MySQL closing idle connections.
Set pool_recycle to deal with MySQL closing idle connections.

See http://docs.sqlalchemy.org/en/latest/dialects/mysql.html#connection-timeouts

Cherry-picking this onto master so it definitely gets deployed.

closeio/nylas,ErinCall/sync-engine,jobscore/sync-engine,nylas/sync-engine,EthanBlackburn/sync-engine,ErinCall/sync-engine,wakermahmud/sync-engine,PriviPK/privipk-sync-engine,wakermahmud/sync-engine,Eagles2F/sync-engine,EthanBlackburn/sync-engine,EthanBlackburn/sync-engine,closeio/nylas,ErinCall/sync-engine,gale320/sync-engine,Eagles2F/sync-engine,nylas/sync-engine,nylas/sync-engine,wakermahmud/sync-engine,jobscore/sync-engine,PriviPK/privipk-sync-engine,Eagles2F/sync-engine,gale320/sync-engine,gale320/sync-engine,EthanBlackburn/sync-engine,EthanBlackburn/sync-engine,jobscore/sync-engine,wakermahmud/sync-engine,gale320/sync-engine,PriviPK/privipk-sync-engine,closeio/nylas,nylas/sync-engine,closeio/nylas,jobscore/sync-engine,PriviPK/privipk-sync-engine,gale320/sync-engine,PriviPK/privipk-sync-engine,ErinCall/sync-engine,ErinCall/sync-engine,wakermahmud/sync-engine,Eagles2F/sync-engine,Eagles2F/sync-engine