Search for and tag FSS oscillations before lockloss

Looks at PSL-FSS_TPD_DC_OUT_DQ for dips below 0.3 within 5 seconds before lockloss and creates tag if it finds any. These FSS-related locklosses are fast, and the glitch is expected to occur very close to the refined lockloss time. For this reason it depends on a strong lockloss refinement, which may preclude LLO from getting good use of this followup.

Example tag: Screen_Shot_2020-02-07_at_3.48.49_PM

Example plot: https://ldas-jobs.ligo-wa.caltech.edu/~yannick.lecoeuche/events/1268/490340/fss.png

Closes #154 (closed)