tm: proper increment of lightweight parsing for call-id

- a pretty much harmless fix to increment with 3 instead of 7 when
  parsing Call-ID name in lightweight parser
- reported and patch by Walter Doekes, FS#168
(cherry picked from commit 21346f47f7712d08369e45e970a6ffec3eab0a3c)

modules/tm/lw_parser.c

@@ -142,7 +142,7 @@ char *lw_get_hf_name(char *begin, char *end,
 
 		case __id1_:
 		case __id2_:
-			p += 7;
+			p += 3;
 			*type = HDR_CALLID_T;
 			break;