Don't use deprecated module commands

The commands module was deprecated since version 2.6 and it has been
removed in Python 3. Use the subprocess module instead.
See http://docs.python.org/2/library/commands#module-commands

Closes-Bug: #1248216
Change-Id: I0a89dbba374a28b16a6e24f2a1b05ce06e044de4
Merge "Don't use deprecated module commands"