LU-11946 build: no zlib check during configure --enable-dist

LU-11946 build: no zlib check during configure --enable-dist

If the zlib libraries are not found, the error is fatal, and prevents
the sources from being packaged.

This check is unnecessary when sources are being packaged, so this patch
disables the test when configure is run with --enable-dist.

Lustre-change: https://review.whamcloud.com/34811
Lustre-commit: e9d9a0eeb0ff71b207e9d0095fce16af74f842b6

Change-Id: Ie262b17b63c0edc8e8bfbd0c1a466ec37d05622c
Signed-off-by: Olaf Faaland <faaland1@llnl.gov>
Reviewed-by: Nathaniel Clark <nclark@whamcloud.com>
Reviewed-by: Minh Diep <mdiep@whamcloud.com>
Signed-off-by: Minh Diep <mdiep@whamcloud.com>
Reviewed-on: https://review.whamcloud.com/35194
Tested-by: Jenkins
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>