MBS-7928: Follow change of search server response format

The recent search server release changed top-level list elements in
responses to consistently be in plural form, e.g. "recordings" instead
of "recording" (SEARCH-383). The release editor still expected the old
(singular) form, however, so it interpreted all recording searches as
returning nothing.
Merge remote-tracking branch 'chirlu/mbs-7928'

* chirlu/mbs-7928:
  MBS-7928: Follow change of search server response format