Fixed typo in run_tests.sh file

Change-Id: I4790478de8eeb7b9207c2395251d679c3530556a

tests/run_tests.sh

@@ -124,7 +124,7 @@ clean() {
 }
 
 salt_run() {
-    [ -e ${VEN_DIR}/bin/activate ] && source ${VENV_DIR}/bin/activate
+    [ -e ${VENV_DIR}/bin/activate ] && source ${VENV_DIR}/bin/activate
     salt-call ${SALT_OPTS} $*
 }