* Add a linux commands config file, rename the old and create a wrapper
  that loads either of these depending on system.
* Replace hardcoded path to /etc/mnttab to MNTTAB from commands.cfg.
* Fix is_physical_device() to recognize devs on Linux.
* Don't set TMPDIR on BSD, they want it in the root dir.
* Set MNTTAB=/etc/mtab on Linux and /etc/mnttab on BSD (to be able to
  use another file in Linux).
* Set the env variable LINUX=1 if it's a Linux system.
Add a test target to the main Makefile.
Add basic makefile for linux to compile ctime_001_pos required by test..
Look for ksh for the test cases.
A script using truncate that will emulate 'mkfile' for the tests.
Test case run file for Linux.
The run script, link to ../cmd/run.py.
Don't create data files in the root - use $TMPDIR ('/var/tmp').
Don't use hardcoded paths and command, use the variables defined in commands.cfg.
* Remove exact path to kill, true and sudo.
* Add .{ksh,sh} to the command to allow to run without installing.
  + Ditto for verifying file name.
* Include default.cfg at the top instead of the bottom (to get command variable defines etc).
* Remove Don't use hardcoded paths and command, use the variables defined in commands.cfg.
* Some stuff isn't relevant on Linux.
* Don't force set STF_{SUITE,TOOLS}. Use value from env if availible.
* Rename find_disks() to find_disks_zfstest() to not clash with one from lib.
Remove unnessesary tests that isn't ZFS related.
Use getent instead of groupmod (which don't exist in Linux) in libtest.shlib:add_group().
* In add_group(), groupadd return 9 if group already exists - re-set it to 4
  to avoid to much clutter in the case.
* Use getent instead of groupmod to find if a group exists or not.
Use LINUX instead of 'uname -a | grep' - faster.