Update ZTS to work on FreeBSD

Update the common ZTS scripts and individual test cases as needed 
in order to allow them to be run on FreeBSD.  The high level goal
is to provide compatibility wrappers whenever possible to minimize
changes to individual test cases.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: Matt Macy <mmacy@FreeBSD.org>
Signed-off-by: Ryan Moeller <ryan@ixsystems.com>
Closes #9692

tests/zfs-tests/include/commands.cfg

@@ -8,22 +8,17 @@
 # Please keep the contents of each variable sorted for ease of reading
 # and maintenance.
 #
-export SYSTEM_FILES='arp
+export SYSTEM_FILES_COMMON='arp
     awk
-    attr
     base64
     basename
     bc
-    blkid
-    blockdev
     bunzip2
     bzcat
     cat
-    chattr
     chgrp
     chmod
     chown
-    cksum
     cmp
     cp
     cpio
@@ -37,11 +32,8 @@ export SYSTEM_FILES='arp
     du
     echo
     egrep
-    exportfs
     expr
-    fallocate
     false
-    fdisk
     file
     find
     fio
@@ -49,15 +41,10 @@ export SYSTEM_FILES='arp
     getconf
     getent
     getfacl
-    getfattr
     grep
-    groupadd
-    groupdel
-    groupmod
     gunzip
     gzip
     head
-    hostid
     hostname
     id
     iostat
@@ -65,29 +52,16 @@ export SYSTEM_FILES='arp
     ksh
     ln
     logname
-    losetup
     ls
-    lsattr
-    lsblk
-    lscpu
-    lsmod
-    lsscsi
-    md5sum
     mkdir
     mknod
-    mkswap
     mktemp
-    modprobe
     mount
-    mpstat
     mv
     net
-    nproc
     od
     openssl
-    parted
     pax
-    perf
     pgrep
     ping
     pkill
@@ -105,11 +79,8 @@ export SYSTEM_FILES='arp
     scp
     sed
     seq
-    setenforce
     setfacl
-    setfattr
     sh
-    sha256sum
     shuf
     sleep
     sort
@@ -130,13 +101,9 @@ export SYSTEM_FILES='arp
     tr
     true
     truncate
-    udevadm
     umask
     umount
     uname
-    useradd
-    userdel
-    usermod
     uuidgen
     vmstat
     wait
@@ -144,6 +111,55 @@ export SYSTEM_FILES='arp
     which
     xargs'
 
+export SYSTEM_FILES_FREEBSD='chflags
+    compress
+    dumpon
+    fsck
+    gpart
+    md5
+    mdconfig
+    mkfifo
+    newfs
+    pw
+    sha256
+    swapctl
+    sysctl
+    uncompress'
+
+export SYSTEM_FILES_LINUX='attr
+    blkid
+    blockdev
+    chattr
+    cksum
+    exportfs
+    fallocate
+    fdisk
+    getfattr
+    groupadd
+    groupdel
+    groupmod
+    hostid
+    losetup
+    lsattr
+    lsblk
+    lscpu
+    lsmod
+    lsscsi
+    md5sum
+    mkswap
+    modprobe
+    mpstat
+    nproc
+    parted
+    perf
+    setenforce
+    setfattr
+    sha256sum
+    udevadm
+    useradd
+    userdel
+    usermod'
+
 export ZFS_FILES='zdb
     zfs
     zhack