Postgres version is not exposed if database discovery is not enabled

[vovka667]

Version v0.6.0:

$ curl -s localhost:9187/metrics | grep static
# HELP pg_static Version string as reported by postgres
# TYPE pg_static untyped
pg_static{server="127.0.0.1:5432",short_version="11.5.0",version="PostgreSQL 11.5 (Ubuntu 11.5-3.pgdg18.04+1) on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 7.4.0-1ubuntu1~18.04.1) 7.4.0, 64-bit"} 1
$ 

Version v0.7.0:

$ curl -s localhost:9187/metrics | grep static
$ 

But it works fine if --auto-discover-databases flag is present.
Probably it was broken in #314

[wrouesnel]

Resolved by #334 hopefully with thanks to @sfalkon