introduced the mount_fs function with 13_include_mount_filesystem_code.sh which
is called from 13_include_filesystem_code.sh; it will allow us to overrule the
generic mount_fs function from distro overruling script;
e.g. layout/prepare/SUSE_LINUX/i386/14_include_mount_filesystem_code.sh could redefine
the function for btrfs purposes.

The generic script contains the btrfs mount code for fedora 20/21 (and it has been tested)

Look into issue #233 for more in-depth information