mysqld_safe not run on RHEL7, while it runs on RHEL6 when starting mariadb
It is stated in the mariadb and even mysql docs:

https://mariadb.com/kb/en/mariadb/systemd/

systemd services are packaged on RPM and Debian based Linux distributions. When systemd is used, mysqld_safe is not used and settings in the mysqld_safe section of configuration files will not be read or applied.

https://dev.mysql.com/doc/refman/5.7/en/server-management-using-systemd.html

On platforms for which systemd support is installed, scripts such as mysqld_safe and the System V initialization script are not installed because they are unnecessary. For example, mysqld_safe can handle server restarts, but systemd provides the same capability, and does so in a manner consistent with management of other services rather than using an application-specific program.