Wrong key location in Debian install instructions

[jarrpa]

The docs (here)[https://github.com/gluster/glusterdocs/blob/master/Install-Guide/Install.md] say that you should at the following GPG key:

http://download.gluster.org/pub/gluster/glusterfs/LATEST/rsa.pub

Unfortunately, there's no such key file there. glusterfs/LATEST appears to just be a link to glusterfs/3.12/LATEST, but the key that you need to use is located at glusterfs/3.12/rsa.pub.

Either the instructions should be updated or some sort of link or duplicate of the required key should be maintained.

[prashanthpai]

PR #305 addresses this.