Fix code warning.

Change-Id: Ib11fb49f528d3688351ae349d5b4e307c28b3967
diff --git a/mbtk/libmbtk_lib/sleep/mbtk_sleep.c b/mbtk/libmbtk_lib/sleep/mbtk_sleep.c
index c2b8be0..25c3997 100755
--- a/mbtk/libmbtk_lib/sleep/mbtk_sleep.c
+++ b/mbtk/libmbtk_lib/sleep/mbtk_sleep.c
@@ -1,5 +1,6 @@
 #include "mbtk_sleep.h"
 #include "mbtk_log.h"
+#include "mbtk_utils.h"
 
 static mbtk_lock_name_s mbtk_lock_name[LOCK_MAX_SIZE]={0};
 
@@ -10,7 +11,7 @@
     {
         if(!access("/sys/power/autosleep", W_OK))
         {
-            system("echo mem > /sys/power/autosleep");
+            mbtk_system("echo mem > /sys/power/autosleep");
             autosleep_enable = TRUE;
             return 0;
         }
@@ -24,7 +25,7 @@
     {
         if(!access("/sys/power/autosleep", W_OK))
         {
-            system("echo off > /sys/power/autosleep");
+            mbtk_system("echo off > /sys/power/autosleep");
             autosleep_enable = FALSE;
             return 0;
         }
@@ -66,7 +67,7 @@
             if(mbtk_lock_name[i].fd == 0)
                 break;
         }
-        
+
         if (i >= LOCK_MAX_SIZE)
         {
             LOGE("Fd is full.");
@@ -101,7 +102,7 @@
     {
         char cmd[128]={0};
         sprintf(cmd, "echo %s > /sys/power/wake_lock", mbtk_lock_name[i].name);
-        system(cmd);
+        mbtk_system(cmd);
         return 0;
     }
     else
@@ -131,7 +132,7 @@
     {
         char cmd[128]={0};
         sprintf(cmd, "echo %s > /sys/power/wake_unlock", mbtk_lock_name[i].name);
-        system(cmd);
+        mbtk_system(cmd);
         return 0;
     }
     else