add ACTION_MSG of LEVEL_ZERO_FM_SUBSYS flashlist to snapshot

[andreh12]

this is needed for item 5 in cmsdaq/DAQExpert#232 but probably also has applications elsewhere

[Phil2812]

You might also want to add the ERROR_MSG parameter, then. Some subsystems propagate their error messages as state change reasons (STATE_CHANGE_REASON parameter in the LV0's subsystem status parameter map; not published to Flashlist) as part of their Error state notification.

[andreh12]

good point @Phil2812 , thanks for mentioning this !