main: fix name of program

Should be lowercase so that --help reports the correct usage details.
Before this it was suggesting running with the uppercase name

BUG=chromium:1127071
TEST=ran it

Change-Id: Ib2a0f3d7eb9e7bc64cf6e96ea65b8d1e8e0050dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/infra/tnull/+/2482022
Tested-by: Sean Abraham <seanabraham@chromium.org>
Auto-Submit: Sean Abraham <seanabraham@chromium.org>
Reviewed-by: Jared Loucks <jaredloucks@google.com>
Commit-Queue: Jared Loucks <jaredloucks@google.com>
diff --git a/src/tnull/main.go b/src/tnull/main.go
index b3edb0e..6f977e6 100644
--- a/src/tnull/main.go
+++ b/src/tnull/main.go
@@ -18,7 +18,7 @@
 
 func main() {
 	application := &cli.Application{
-		Name:  "TNull",
+		Name:  "tnull",
 		Title: "A minimal Remote Test Driver for testing API and faking out aspects of the RTD for meta-testing purposes.",
 		Context: func(ctx context.Context) context.Context {
 			return gologger.StdConfig.Use(ctx)