Better UNIX-socket access rights policy
Better UNIX-socket access rights policy

Change UNIX-socket's group access rights only if "run as guid" has been
specifically requested. Otherwise that change might constitute mild
security risk for existing deployments, i.e. we are breaking POLA by
introducing ability to use socket to group users, where there has been
none previously.

See Maksym's note no.1:

* https://github.com/sippy/rtpproxy/pull/10#issuecomment-60554402

Signed-off-by: Peter Lemenkov <2f981fc861bda8c748898150c942841af4296212@gmail.com>

jevonearth/rtpproxy,jevonearth/rtpproxy,synety-jdebp/rtpproxy,sippy/rtpproxy,dsanders11/rtpproxy,Vocalocity/rtpproxy-pre,sippy/rtpproxy,Vocalocity/rtpproxy-pre,hongbinz/rtpproxy,Vocalocity/rtpproxy-pre,synety-jdebp/rtpproxy,synety-jdebp/rtpproxy,dsanders11/rtpproxy,Vocalocity/rtpproxy-pre,jevonearth/rtpproxy,hongbinz/rtpproxy,hongbinz/rtpproxy,synety-jdebp/rtpproxy,jevonearth/rtpproxy,dsanders11/rtpproxy,sippy/rtpproxy,hongbinz/rtpproxy