Fixed mac helper stub issues.

Change-Id: I00114e2ad134af85f97eedbf390b67de3f522b58

Author: Juha Heiskanen

test/nanostack/unittest/6lp_mac/mac_helper/test_mac_helper.c

@@ -642,6 +642,7 @@ bool test_mac_helper_mac_channel_set()
     protocol_interface_info_entry_t entry;
     memset(&entry, 0, sizeof(protocol_interface_info_entry_t));
     arm_15_4_mac_parameters_t params;
+    memset(&params, 0, sizeof(arm_15_4_mac_parameters_t));
     entry.mac_parameters = &params;
     mac_api_t api;
     api.mlme_req = &mlme_req;
@@ -659,6 +660,7 @@ bool test_mac_helper_write_our_addr()
     protocol_interface_info_entry_t entry;
     memset(&entry, 0, sizeof(protocol_interface_info_entry_t));
     arm_15_4_mac_parameters_t params;
+    memset(&params, 0, sizeof(arm_15_4_mac_parameters_t));
     entry.mac_parameters = &params;
     sockaddr_t addr;
     addr.addr_type = ADDR_NONE;
@@ -766,6 +768,7 @@ bool test_mac_helper_frame_overhead()
 
 bool test_mac_helper_link_frame_counter_read()
 {
+    protocol_core_stub.entry_ptr = NULL;
     if( -1 != mac_helper_link_frame_counter_read(0, NULL) ){
         return false;
     }