plugin pubsub cache: avoid race condition by retrying node request: When retrieving items, there may be a race condition if a node is not found in cache, then created before `setPubsubNode` is called. This patch handle this case by retrying in case of UNIQUE constraint violation.

FROM libervia/prosody:e2e

LABEL maintainer="Goffi <tmp_dockerfiles@goffi.org>"

RUN prosodyctl register demo server1.test demo