res_config_ldap: Fix erroneous LDAP_MOD_REPLACE in LDAP modify

We always treat the first change of our modification batch as a
replacement when it sometimes is actually a delete. So we have to pass
the correct arguments to the OpenLDAP library.

ASTERISK-26580 #close
Reported by: Nicholas John Koch
Patches:
	res_config_ldap.c-11.24.1.patch (license #6833) patch uploaded
	by Nicholas John Koch

Change-Id: I0741d25de07c9539f1edc6eff3696165dfb64fbe