tests/test_runner.sh: remove some redundancies

This wrapper doesn't need to load anything from helpers.bash, because
the various .bats files already do so on their own.

Signed-off-by: Nalin Dahyabhai <nalin@redhat.com>

tests/test_runner.sh

@@ -7,16 +7,10 @@ cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"
 # labels than /tmp, which is often on tmpfs.
 export TMPDIR=${TMPDIR:-/var/tmp}
 
-# Load the helpers.
-. helpers.bash
-
 function execute() {
 	>&2 echo "++ $@"
 	eval "$@"
 }
 
-# Tests to run. Defaults to all.
-TESTS=${@:-.}
-
 # Run the tests.
-execute time bats --tap $TESTS
+execute time bats --tap "${@:-.}"