mariadb: 10.2.16 -> 10.2.17 (#45199)

Bump to latest stable version of the 10.2.x branch. Besides many bug fixes the
following security related issues have been fixed:
 - CVE-2018-3060
 - CVE-2018-3064
 - CVE-2018-3063
 - CVE-2018-3058
 - CVE-2018-3066

Release notes: https://mariadb.com/kb/en/library/mariadb-10217-release-notes/