TT#18774 Migrate NGCP from sysv to systemd, mysqld_safe

In short, this script/process is unneeded in systemd-based systems, so
it has been removed.

From https://dev.mysql.com/doc/mysql-linuxunix-excerpt/5.7/en/using-systemd.html :

  On platforms for which systemd support for MySQL is installed,
  scripts such as mysqld_safe and the System V initialization script
  are unnecessary and are not installed. 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 by using an application-specific program.

  Because systemd has the capability of managing multiple MySQL
  instances on platforms for which systemd support for MySQL is
  installed, mysqld_multi and mysqld_multi.server are unnecessary and
  are not installed.

Change-Id: I1536844a3ed67e153bd986d940bfeea088e978e7

templates/400_process-debian.yaml.tt2

@@ -15,7 +15,7 @@ process:
     running: true
 
   mysqld_safe:
-    running: true
+    running: [% general.init_system == 'systemd' ? 'false' : 'true' %]
 
   nginx:
     running: true