Revert "Declare visibility for class properties in MySQLMasterPos"

These members are accessed from DatabaseMysqlBase::masterPosWait and
DatabaseBase::masterPosWait, causing errors if the wiki has slave
databases or has fakeSlaveLag set.

This reverts commit d0325927d4a7352590e52690aa30ce63fffb6ab8.

Change-Id: I563bde457274dad2f254145426376b275b597e2a
Merge "Revert "Declare visibility for class properties in MySQLMasterPos""