Use 'replica' instead of 'slave'

Replace the mysql-specific term 'slave' with the more general term
'replica'.

Change-Id: Id22d18a84a4ac104ff8af09959e8eb2ae0102e97
Depends-On: Ief4bc83369fa3183a321d3e07b69b1801595ab15
Closes-Bug: 1360310