Fix init script

The place where easy_install puts entry points is not necessarily in
init's PATH, so read it from /etc/default/taf since we ask the user for
it anyway.
Fix up for open source pyvmomi

Depend on pyvmomi>=4.1.0 instead of pySdk (bad public name...)
However, the internal one we depended upon before used different casing
for API stuff... so fix that.