create_command_string check len(pos_parms) and filter(None, pos_parms)
create_command_string check len(pos_parms) and filter(None, pos_parms)

- Make sure pos_parms has entries before trying to reference last entry.
- Filter blank/None pos_parms entries out when forming command_string.

Change-Id: I4e2315f0ce33a18c00ea1c06c7531e1e04cc004f
Signed-off-by: Michael Walsh <10404802c7de463f402c4a18638106ca1b12ef61@us.ibm.com>

openbmc/openbmc-test-automation,openbmc/openbmc-test-automation