Fixes private functions private

Fixed functions below to private APIs.

raise_if_duplicate_entry_error()
raise_if_deadlock_error()
wrap_db_error()
synchronous_switch_listener()
add_regexp_listener()
greenthread_yield()
ping_listener()
is_db_connection_error()
patch_mysqldb_with_stacktrace_comments()

Fixes bug #1119709

Change-Id: I61f700cdbae0126a8b89f6895e4332d695191dd0