I notice on installing maxscale-1.4.3.1-1 (rpm) on CentOS 6:

[user@host ~]$ sudo rpm -Uvh maxscale-1.4.3.1-1.centos.6.x86_64.rpm
warning: maxscale-1.4.3.1-1.centos.6.x86_64.rpm: Header V4 RSA/SHA1 Signature, key ID 8167ee24: NOKEY
Preparing... ########################################### [100%]
1:maxscale ########################################### [100%]
which: no systemctl in (/sbin:/bin:/usr/sbin:/usr/bin:/usr/X11R6/bin)
[user@host ~]$

You use "which" to find something, but I think you're missing a '2>/dev/null' somewhere.

On CentOS 6 systemctl does not exist, as it uses the old (traditional init scripts).

I'm not sure if this breaks anything but certainly the install should I think be silent.