The zlib1g-dev is installed indirectly for Ubuntu 12.04 or Ubuntu 14.04
but it is only suggested in Debian/jessie. Adding it to the
Build-depends is redundant and harmless for Ubuntu and resolves the
missing dependency for Debian.
http://tracker.ceph.com/issues/11068Fixes: #11068
Signed-off-by: Loic Dachary <ldachary@redhat.com>