Ticket #47419 - Unhashed userpassword can accidentally get removed from mods

Bug description:
Change made in commit 4305deeaa41ea8703ebb9ea6529790dd609b3060
sets LDAP_MOD_IGNORE to unhashed password in mods once it's
stashed in an entry extenstion.  It could be freed any time
once pack_mods is called.

Fix description: This patch stops setting LDAP_MOD_IGNORE to
unhashed password in mods.

https://fedorahosted.org/389/ticket/47419

Reviewed by Nathan (Thank you!!)

ldap/servers/slapd/entry.c

@@ -3503,7 +3503,6 @@ slapi_entry_apply_mod_extension(Slapi_Entry *e, const LDAPMod *mod, int modcnt)
                 rc = 0;
                 break;
             }
-            ((LDAPMod *)mod)->mod_op = LDAP_MOD_IGNORE; /* we don't need it any more */
         }
     }
 bail: