net-test: add -b to mean --builder

Faster to type and takes less space on command line.
-b could also be interpreted as 'batch' mode (or non interactive mode).

Test: yes
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I7aec3a70d66dd0aae35cd697954d55cf48541a66
diff --git a/net/test/run_net_test.sh b/net/test/run_net_test.sh
index 606c749..c01c6ea 100755
--- a/net/test/run_net_test.sh
+++ b/net/test/run_net_test.sh
@@ -133,7 +133,7 @@
 fi
 
 while [[ -n "$1" ]]; do
-  if [[ "$1" == "--builder" ]]; then
+  if [[ "$1" == "--builder" || "$1" == "-b" ]]; then
     consolemode="con=null,fd:1"
     testmode=builder
     shift