Log deploy_utils.deploy() erros in the PXE driver

When the PXE driver invoke deploy_utils.deploy() it wasn't logging the
exceptions raised by this call. There was a comment saying that it was
being logged within the deploy() method itself, but it wasn't true for
all the exceptions it could raise, also, some of errors e.g TypeError
where not all parameters are being passed to the deploy() function can't
be logging by the function called itself and would fail silently. So
this patch is adding a log in the PXE module to fix this problem.

Change-Id: Ifbbc0f3cbd5c280d04249cee811d1dc478548975
Closes-Bug: #1286053
Merge "Log deploy_utils.deploy() erros in the PXE driver"