test: Refactor arg parsing for the run script

Tidy up this code a little. Also use '-k' consistently, since -m is more
limited in what it can accept.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/test/run b/test/run
index 869406c..0c8aeb5 100755
--- a/test/run
+++ b/test/run
@@ -13,9 +13,12 @@
 	[ $? -ne 0 ] && failures=$((failures+1))
 }
 
-# SKip slow tests if requested
-[ "$1" == "quick" ] && mark_expr="not slow"
-[ "$1" == "quick" ] && skip=--skip-net-tests
+# Select test attributes
+if [ "$1" = "quick" ]; then
+	mark_expr="not slow"
+	skip=--skip-net-tests
+fi
+
 [ "$1" == "tools" ] && tools_only=y
 
 failures=0
@@ -23,7 +26,7 @@
 if [ -z "$tools_only" ]; then
 	# Run all tests that the standard sandbox build can support
 	run_test "sandbox" ./test/py/test.py --bd sandbox --build \
-		-m "${mark_expr}"
+		-k "${mark_expr}"
 fi
 
 # Run tests which require sandbox_spl