GUACAMOLE-919: pass through defaultStatementTimeout

Testing a workaround for handling dropped TCP connections to the Postgres database.

guacamole-docker/bin/start.sh

@@ -354,6 +354,10 @@ END
         "postgresql-default-max-group-connections-per-user" \
         "$POSTGRES_DEFAULT_MAX_GROUP_CONNECTIONS_PER_USER"
 
+    set_optional_property               \
+        "postgresql-default-statement-timeout" \
+        "$POSTGRES_DEFAULT_STATEMENT_TIMEOUT"
+
     set_optional_property          \
         "postgresql-user-required" \
         "$POSTGRES_USER_REQUIRED"