wlan: Fix for IBSS ping failures

Ping failures were observed when the security mode was changed
from open to secure and vice-versa.

Change-Id: Icfe56b963b60a7937e07737039a995a1bb57d151
CRs-Fixed: 567719
diff --git a/CORE/HDD/src/wlan_hdd_cfg80211.c b/CORE/HDD/src/wlan_hdd_cfg80211.c
index 1d68540..688ee56 100644
--- a/CORE/HDD/src/wlan_hdd_cfg80211.c
+++ b/CORE/HDD/src/wlan_hdd_cfg80211.c
@@ -6331,6 +6331,7 @@
     ENTER();
 
     pWextState->wpaVersion = IW_AUTH_WPA_VERSION_DISABLED;
+    vos_mem_zero(&pHddStaCtx->ibss_enc_key, sizeof(tCsrRoamSetKey));
 
     if (params->ie_len && ( NULL != params->ie) )
     {