EX-7601 osc: add COMPR_GAP check to compress_request

EX-7601 osc: add COMPR_GAP check to compress_request

Currently, compress_request will build the compression
buffer (calling merge_chunk()) for requests which are less
than the minimum compression gap.  This is noticed in the
compression code when it checks if there's enough data to
attempt compression, but we can do a trivial check in
compress_request() to save that work.

Also fix a few minor style things.

This is not an important fix, but I discovered it while
investigating another issue and it's trivial to resolve.

Signed-off-by: Patrick Farrell <pfarrell@whamcloud.com>
Change-Id: Ieb32e6297e10d229f23c58e2ef4d933ce3dda4f2
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/53587
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Artem Blagodarenko <ablagodarenko@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>