firmware_update: Add check when ui calls RequestUpdates

Add a check to differentiate if GetUpdates is called when the UI is
opened or automatically (usb insert or during boot).

BUG=b:328637488
TEST=autoninja chrome; manually check from logs
     interactive_ui_tests --gtest_filter=*FirmwareUpdateInteractiveUi*;

Change-Id: Ib8a92bf0a3e23b6c8f03740e1e07ce4d0c112920
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5367599
Commit-Queue: Rishabh Agrawal <rishabhagr@chromium.org>
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1279078}