Fix test output when gzip is run with -tlv

[thj]

Summary

When run with test, verbose and list we need to parse the file otherwise
the test output is "NOT OK" even for valid files

Test Plan

Create a test file, gzip and xz it. gzip -tlv will report "NOT OK" when
testing the file before and "OK" after.

$ dd if=/dev/random bs=1m count=1 | b64encode - > 1M.out
$ gzip 1M.out
$ xz -z 1M.out
$ gunzip -tlv ~/tmp/1M.out.xz
     1089356      1416525  23.0% /home/tj/tmp/1M.out.xz
/home/tj/tmp/1M.out.xz:   NOT OK
$ gunzip -tlv ~/tmp/1M.out.gz
method  crc     date  time    compressed uncompressed  ratio uncompressed_name
defla 563d46f5 Jan 26 11:39      1077905      1077550  -0.1% /home/tj/tmp/1M.out
/home/tj/tmp/1M.out.gz:   NOT OK

[kevans]

I don't see any use in nanobsd or freebsd-wifi-build

[kevans]

In D34046#769825, @kevans wrote:

I don't see any use in nanobsd or freebsd-wifi-build

Whoops; wrong review, right comment. (approval was correct, though)

[allanjude]

Reviewed By: allanjude

usr.bin/gzip/gzip.c

1660

Should we be doing close(fd) here?