WL#7150: Remove use of DATADIR in mysqld_safe for setting MYSQL_HOME in 5.7

Affects: Server-5.7   —   Status: Complete

The use of DATADIR in mysqld_safe for setting MYSQL_HOME has been deprecated
earlier (a warning had existed since 5.0) and will now be removed.


User Documentation
==================

http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-8.html
http://dev.mysql.com/doc/refman/5.7/en/option-files.html