Allow for conf-based control of auto-mounting glusterfs volume

Introduce a fs.glusterfs.automount configuration parameter, defaulting
to true, which when set to false will skip exec(mount ...) during
initialization.

Signed-off-by: Matthew Farrellee <matt@redhat.com>
Merge pull request #6 from mattf/configurable-automount

Allow for conf-based control of auto-mounting glusterfs volume