Fix uninstall error on debian (port to .SPEC)

Because of "set -e", we need to test if cf-* processes are running before
killing them, otherwise postrm fails and we cannot uninstall the package.
Merge pull request #140 from CedricCabessa/contrib

Fix uninstall error on debian (port to .SPEC)
Merge branch 'branches/rudder/2.4' into branches/rudder/2.6
Merge branch 'branches/rudder/2.6' into branches/rudder/2.7