Fixed: Short-circuit the LDAP sync if LDAP is disabled

[snipe]

Previously, even if LDAP was disabled in the LDAP settings, if a cron was set up to sync, we would still sync, since we weren't checking to see if LDAP was enabled. This should resolve that issue.

[what-the-diff]

• Added a check to see if LDAP is enabled. If it isn't, then the script will abort and display an error message
• Changed ini_set() calls from using env('LDAP_TIME_LIM', 600) to use Setting::getSettings()->ldap instead of hardcoded values

[uberbrady]

I can't possibly imagine a situation where someone has "LDAP enabled" set to off and yet is using LDAP to do syncs, so I think this should be a pretty reasonable change. If we start to see blowback from it, maybe we can figure out a way to mess around with it. But good catch, and it makes total sense to me.

[snipe]

@uberbrady the use-case is for our hosted customers. If they have LDAP disabled (for example, because they are trying to sort out some settings, or username formats, but they have a sync cron running.)