Ensure strand is only posted to in GET mode

We should only use strands for GET requests.

Otherwise we can crash in Dbus Call sending.

Tested: No longer crashes on POST request

Google-Bug-Id: 408303287
Change-Id: Id32ba154345589dab1db4d78c28fc251c054006a
Signed-off-by: Edward Lee <edwarddl@google.com>
diff --git a/gbmcweb b/gbmcweb
index 7db5270..2eec22d 160000
--- a/gbmcweb
+++ b/gbmcweb
@@ -1 +1 @@
-Subproject commit 7db52705e4a3e5d886c86c5d9ae5958010a9cbc8
+Subproject commit 2eec22d35f741e1410ee878eb69621da816acd22