Can not use `info` logging level from docker image

[dpordomingo]

caused by https://github.com/src-d/sourced-ce/issues/142

Under the context UX on source{d} CE, I'm reviewing its logs (to make them as simple as possible, to be understandable for the user), and I saw that for gitbase, is not possible to use debug level info (info, which is the default for gitbase, is the only one failing, the others are not)

I found that it's because the verbose mode is enabled in the init.sh, so when using gitbase docker image, the debug level is set from the beginning by server.go:131, and since it was passed info to the command (the default), it is not recovered because of the if at server.go:140

If it is requested any other log level, the if at server.go:140 will let that the desired log level is used.

[dpordomingo]

proposed solution:
#935