img.install: Fixing NONETWORKTEST feature

The variable wasn't properly leading to a non existing variable in the
code.

As a result, the parameter was useless
health-check: Adding psutil and gcc

When running under RHEL6.5, we need psutil to be installed for python
2.7. This does requires gcc to works well.
init.health: Fixing NONETWORKTEST

Oops, that should have been part of commit 05dc7bafdae92e92cb9a2048e387168d10201148
init: Using python 2.7 wrapper

When running under RHEL6.5 we need to use the python trick.
So let's put this into a function do_python and call it when we have to
run some python code.
init: Silencing unless error messages

As we try two options, let's silence the one that fail.
health-check: Fixing file naming

The output file was badly named "*.hw_".
The trailing underscore is clearly useless