Add default configuration path

[kenji114]

Although the QUICKSTART says the lagopus.conf can be located in a /etc/lagopus/ directory, it does not look for it in such directory. Only /usr/local/etc/lagopus/lagopus.conf is available as a local configuration path with the default ./configure option other than the file in the current directory.

[ynkjm]

Hi @kenji114

Thanks your pull request but we reject this pull request.
The previous QUICKSTART has several wrong stuff, so we have fixed the QUCIKSTART.
And current lagopus daemon option provide for users to specify configuration path with -C filename or `--config filename``.

Thanks,