Add read_timeout and infinite retries to MySQL conns

read_timeout=60 is an explicit parameter added
for mysqldb to bail connections if no data is
received for 60s. Depends on MySQLdb 1.2.5
max_retries=-1 for all connections so that
APIs don't give up and die

Change-Id: Ib4a2cdcc287cbc53c18f7500d96f82d8099e0f35
Partial-Bug: #1285449