Add pylint-based lintstack test to tox environment

lintstack is a pylint-based static analysis tool to find bugs
in Python code.

To run the test via tox: $ tox -e pylint
To run the test directly: $ tools/lintstack.sh

Change-Id: If155f47ed84eb820ac505ee741bdd18edd41b1eb
Merge "Add pylint-based lintstack test to tox environment"
Add missing spaces to iscsi_iotype help

Missing spaces cause the auto-generated sample conf to not look
right.

Change-Id: I8e1b588d7cf18147aa403f0e7391f9c6ae390a6b
Merge "Add missing spaces to iscsi_iotype help"