Precondition:
LDAP settings already exist.

Steps to reproduce:

1. Disable LDAP setting:
   1.  Administration -> Authentication -> LDAP settings
   2. Uncheck "Enable LDAP authentication" and click button "Update"
2. Make changes at LDAP setting:
   1. Check "Enable LDAP authentication"
   2. Change "Port" to another correct value for this connection
   3. Click button 'Update'; 
        Result: Nothing happens. No message text about result.
3. Open another zabbix page
4. Open LDAP settings
     Result: Changes didn't save
     Expected: Changes saved in DB