fs_mgr: overlayfs: test: triage data missing after failure flash scratch

After flashing empty image to scratch device, the device did not
return after 3 minutes.  It also did not collect any triage data
reporting only:

[  FAILED  ] did not reboot after flash

Add triage data, increase timeout to 4 minutes.

Test: adb-remount-test.sh
Bug: 132070014
Change-Id: Ic607abb5b2575d630bf6c27817a38a90820d24e1