Merge 5.5.55 to 5.5-galera

Steps:

• https://github.com/codership/mysql-wsrep/tree/5.5 Merge revisions:
  • 546a1ca0660
  • 8fa05e3dbf7
  • 3ebc60d8d2d
  • 328ade03d4d
  • 9d31fa282ec
  • 0e800a6d9b6
  • 03c22517c87
• Test and ask review
• https://github.com/MariaDB/server/tree/5.5 Merge tag mariadb-5.5.55 (when released)
• Test
• Create tag mariadb-galera-5.5.55
• Create todo for dbart to release