Changed the status check for BleObserve

Bta layer was expecting a successful BLEObserver return status to be BTM_SUCCESS.
Instead BleObserve returns BTM_CMD_STARTED when the scanning is successfully
started. Changed the check to be BTM_CMD_STARTED instead

bug 15167442

Change-Id: Ia600da7e6416e2caef5d34dba24955ae76d06dcc
diff --git a/bta/dm/bta_dm_act.c b/bta/dm/bta_dm_act.c
index 62a977e..7da190a 100644
--- a/bta/dm/bta_dm_act.c
+++ b/bta/dm/bta_dm_act.c
@@ -5164,7 +5164,7 @@
         /*Save the  callback to be called when a scan results are available */
         bta_dm_search_cb.p_scan_cback = p_data->ble_observe.p_cback;
         if ((status = BTM_BleObserve(TRUE, p_data->ble_observe.duration,
-                                bta_dm_observe_results_cb, bta_dm_observe_cmpl_cb))!= BTM_SUCCESS)
+                            bta_dm_observe_results_cb, bta_dm_observe_cmpl_cb))!= BTM_CMD_STARTED)
         {
             tBTA_DM_SEARCH  data;
             APPL_TRACE_WARNING2(" %s BTM_BleObserve  failed. status %d",__FUNCTION__,status);