-Wmaybe-uninitialized sql_planner.cc compilation warnings

[Laurynas Biveinis]

Copy of https://bugs.mysql.com/bug.php?id=77637:

/root/mysql-5.6.25/sql/sql_planner.cc: In member function ‘void Optimize_table_order::best_access_path(JOIN_TAB*, table_map, uint, bool, double, POSITION*, POSITION*)’:
/root/mysql-5.6.25/sql/sql_planner.cc:431: warning: ‘loose_scan_opt.Loose_scan_opt::best_loose_scan_start_key’ may be used uninitialized in this function
/root/mysql-5.6.25/sql/sql_planner.cc:431: warning: ‘loose_scan_opt.Loose_scan_opt::best_max_loose_keypart’ may be used uninitialized in this function
/root/mysql-5.6.25/sql/sql_planner.cc:431: warning: ‘loose_scan_opt.Loose_scan_opt::best_loose_scan_records’ may be used uninitialized in this function
/root/mysql-5.6.25/sql/sql_planner.cc:431: warning: ‘loose_scan_opt.Loose_scan_opt::best_loose_scan_key’ may be used uninitialized in this function
/root/mysql-5.6.25/sql/sql_planner.cc:431: warning: ‘loose_scan_opt.Loose_scan_opt::quick_max_loose_keypart’ may be used uninitialized in this function

[Przemyslaw Skibinski (pskibinski)]

Fixed with https://github.com/percona/percona-server/pull/2079

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-3632