scripts: Fix FLAGS_moblab usage.

Define the usb_devices and moblab flags in the lib/cros_vm_lib
script rather than in bin/cros_start_vm as they are only used
with lib/cros_vm_lib.

BUG=chromium:550695
TEST=Tested running the script.

Change-Id: I3715cafe9b4c47db5b7d9e72edee723745b25417
Reviewed-on: https://chromium-review.googlesource.com/310282
Commit-Ready: Matthew Sartori <msartori@chromium.org>
Tested-by: Matthew Sartori <msartori@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
diff --git a/bin/cros_start_vm b/bin/cros_start_vm
index ee3dc8b..128f903 100755
--- a/bin/cros_start_vm
+++ b/bin/cros_start_vm
@@ -16,11 +16,6 @@
 DEFINE_string board "${DEFAULT_BOARD}" \
     "Board for VM image (unnecessary if path given)"
 DEFINE_string image_path "" "Full path of the VM image"
-DEFINE_string usb_devices "" \
-    "Usb devices for passthrough. Specified in a comma-separated list
-     where each item is of the form <vendor_id>:<product_id>
-     (eg. --usb_devices=1050:0211,0409:005a)"
-DEFINE_boolean moblab ${FLAGS_FALSE} "Setup environment for moblab"
 
 set -e
 
diff --git a/lib/cros_vm_lib.sh b/lib/cros_vm_lib.sh
index 3c957f7..b1f1678 100644
--- a/lib/cros_vm_lib.sh
+++ b/lib/cros_vm_lib.sh
@@ -21,6 +21,11 @@
     "Path to the private key to use to ssh into test image as the root user."
 DEFINE_string vnc "" "VNC Server to display to instead of SDL "\
 "(e.g. pass ':1' to listen on 0.0.0.0:5901)."
+DEFINE_string usb_devices "" \
+    "Usb devices for passthrough. Specified in a comma-separated list
+     where each item is of the form <vendor_id>:<product_id>
+     (eg. --usb_devices=1050:0211,0409:005a)"
+DEFINE_boolean moblab ${FLAGS_FALSE} "Setup environment for moblab"
 
 KVM_PID_FILE=/tmp/kvm.$$.pid
 LIVE_VM_IMAGE=