Disable zpool-layout distribution.

Disable zpool-layout distribution.

Resolve this lintian warning by disabling the zpool-layout example:

W: zfsutils: executable-not-elf-or-script usr/libexec/zfs/zpool-layout/dragon.llnl.conf
W: zfsutils: executable-not-elf-or-script usr/libexec/zfs/zpool-layout/dragon.ddn.conf
N:
N:    This executable file is not an ELF format binary, and does not start
N:    with the #! sequence that marks interpreted scripts. It might be a sh
N:    script that fails to name /bin/sh as its shell, or it may be incorrectly
N:    marked as executable. Sometimes upstream files developed on Windows are
N:    marked unnecessarily as executable on other systems.
N:
N:    If you are using debhelper to build your package, running dh_fixperms
N:    will often correct this problem for you.
N:
N:    Refer to Debian Policy Manual section 10.4 (Scripts) for details.
N:
N:    Severity: normal, Certainty: certain
N: