Return correct value for services that must be enabled in Systemd, not in SysV

This fixes situations, when a server switched from SysV to Systemd.
SysV symlinks are still in place and Salt incorrectly determines, that
service is already enabled.

For example:
~$ salt-call --local service.enabled spamassassin
[INFO    ] Executing command 'systemctl is-enabled spamassassin.service'
[INFO    ] Executing command 'runlevel' in directory '/root'
local:
    True

However:

~$ systemctl is-enabled spamassassin.service
disabled

~$ find /etc/rc*.d/ -name
'*spamassassin'
/etc/rc0.d/K02spamassassin
/etc/rc1.d/K02spamassassin
/etc/rc2.d/S02spamassassin
/etc/rc3.d/S02spamassassin
/etc/rc4.d/S02spamassassin
/etc/rc5.d/S02spamassassin
/etc/rc6.d/K02spamassassin

salt/modules/systemd.py

@@ -779,9 +779,11 @@ def enabled(name, **kwargs):  # pylint: disable=unused-argument
         # string will be non-empty.
         if bool(__salt__['cmd.run'](cmd, python_shell=False)):
             return True
-    else:
+    elif name in _get_sysv_services():
         return _sysv_enabled(name)
 
+    return False
+
 
 def disabled(name):
     '''