Always pass str to shlex.split for py26 compat

On python 2.6 shlex.split cannot handle unicode,
which can lead to TypeError exception.

Details can be seen in
http://bugs.python.org/issue6988
and
http://bugs.python.org/issue1548891

As best solution it seems to decode *cmd* to utf-8 str
before passing to shlex.split().

Change-Id: If56a6f16ab712691b26035d0cd3d7d70260a64c6
Merge "Always pass str to shlex.split for py26 compat"