Fix container build --all. #215.

We didn't need to add an arg check here because it's already there.

internal/app/wwctl/container/build/build_test.go

@@ -0,0 +1,20 @@
+package build
+
+import (
+	"testing"
+)
+
+// TestArgsContainerBuild is a regression test for 215.
+func TestArgsContainerBuild(t *testing.T) {
+	command := GetCommand()
+
+	err := command.Args(command, []string{})
+	if err != nil {
+		t.Errorf("no arguments to container build should succeed.")
+	}
+
+	err = command.Args(command, []string{"container1", "container2"})
+	if err != nil {
+		t.Errorf("multiple arguments to container build should succeed.")
+	}
+}