gunixmounts: Don't treat ZFS as a system internal fs

ZFS was originally added to the list of system internal filesystems by
commit 4cafadc9.

The rationale from https://bugzilla.gnome.org/show_bug.cgi?id=542156
doesn't seem very solid, and now we have x-gvfs-hide for this.

Also, this may contribute for trash:/// ignoring `{zfs mount path}/.Trash/`

So, remove zfs from the ignore_fs array.

Closes #1599
13 jobs for 1599-follow-up-from-gunixmounts-stop-considering-cifs-nfs-as-system-file-systems in 18 minutes and 18 seconds (queued for 4 seconds)
Status Job ID Name Coverage
  Build
passed #155207
cross-android_api21_arm64

00:01:11

passed #155208
cross-android_api28_arm64

00:02:49

passed #155209
cross-mingw64

00:01:39

passed #155206
fedora-autotools-x86_64

00:05:11

passed #155205
fedora-x86_64

00:05:24

failed #164898
freebsd-11
freebsd-11-x86_64

00:04:43

passed #155210
win32
msys2-mingw32

00:07:53

passed #155211
win32
vs2017-x64

00:07:59

failed #162570
freebsd-11
freebsd-11-x86_64

00:04:20

failed #162349
freebsd-11
freebsd-11-x86_64

00:04:33

failed #162216
freebsd-11
freebsd-11-x86_64

00:04:50

failed #155212
freebsd-11
freebsd-11-x86_64

00:04:34

 
  Coverage
skipped #155213
coverage
 
Name Stage Failure
failed
freebsd-11-x86_64 Build
TIMEOUT:    0

Full log written to /var/tmp/gitlab_runner/builds/3fe11159/0/GNOME/glib/_build/meson-logs/testlog.txt
Uploading artifacts...
_build/config.h: found 1 matching files
_build/glib/glibconfig.h: found 1 matching files
_build/meson-logs: found 4 matching files
Uploading artifacts to coordinator... ok id=164898 responseStatus=201 Created token=StroNGxg
ERROR: Job failed: exit status 1