case-lib: hijack.sh use trap to hijack exit command

use 'trap' command hijack exit command instead of function
'exit' which perpare for 'set -e'

Signed-off-by: Wu, BinX <binx.wu@intel.com>

Author: Bin-QA

case-lib/hijack.sh

@@ -2,8 +2,9 @@
 
 SUDO_CMD=$(command -v sudo)
 
+trap 'func_hijack_exit' EXIT
 # Overwrite other functions' exit to perform environment cleanup
-function exit()
+function func_hijack_exit()
 {
     local exit_status=${1:-0}
 
@@ -77,6 +78,7 @@ function exit()
         ;;
     esac
 
+    trap '' EXIT
     builtin exit $exit_status
 }