[ipaccess] Handle LoadAbort coming from the BTS.

* Be bale to abort the load when the BTS is rejecting the file..
diff --git a/openbsc/src/abis_nm.c b/openbsc/src/abis_nm.c
index 8b3ac9c..211f70e 100644
--- a/openbsc/src/abis_nm.c
+++ b/openbsc/src/abis_nm.c
@@ -1568,6 +1568,12 @@
 				rc = sw_load_end(sw);
 			}
 			break;
+		case NM_MT_LOAD_ABORT:
+			if (sw->cbfn)
+				sw->cbfn(GSM_HOOK_NM_SWLOAD,
+					 NM_MT_LOAD_ABORT, mb,
+					 sw->cb_data, NULL);
+			break;
 		}
 		break;
 	case SW_STATE_WAIT_ENDACK: