Log DB version at info level (#1926)
Log DB version at info level (#1926)

This allows for useful diagnostics when digging into issues such as #1845, providing the correct commandline args are provided. e.g:

`go test -v ./storage/mysql/... -count 1 -args -stderrthreshold=INFO`
AlCutter/trillian,google/trillian,RJPercival/trillian,gdbelvin/trillian,google/trillian,AlCutter/trillian,gdbelvin/trillian,RJPercival/trillian,gdbelvin/trillian