Add and fix NginxLiveTest

- Test nginx on different platforms (debian, etc)
- Fix Nginx install on debian: if gcc already installed on standard
  distro, don't try to install it because caused `apt-get install`
  to fail.
Add SoftwareProcessEntityTest.testReleaseEvenIfErrorDuringStart

- Trying to reproduce problem where VM left running in aws-ec2
  by nginx; but clearly this wasn't it.
- And tidies test with setUp/tearDown methods.
Rename NginxAmazonTest to NginxWebClusterEc2LiveTest