lib/test_net.sh: add network help script

Add tst_rhost_run() library function to run commands on remote host.
Supported options:
-b run in background
-s safe option, if something goes wrong, will exit with TBROK
-c specify command to run

Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
ltpstress.sh: added a cmdline option to set temporary directory

Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>
ltpstress.sh: explicit passing of -p and -q ltp-pan parameters

Added cmdline options to pass -p and/or -q arguments to the
ltp-pan instances. The same way as runltp does.

It's needed if we parse the output of the ltp-pans by scripts.

Signed-off-by: Stanislav Kholmanskikh <stanislav.kholmanskikh@oracle.com>