Fix offline store choking by bypassing plugin for redis ops (#63)

* chore: instrument plugin call until redis call

* spike: bypass plugin for offline store

* fix: offline store choking due to blocking redis call through plugin

* chore: format changes

* fix: msg store read fn dialyzer error

* fix: username pass type in vmq_message_store

* chore:fmt changes

Author: dhruvjain99