Clean up the Mantid.user.properties file changes after Jenkins build script has run regardless of success

[Pasarus]

There is an issue where developing Jenkins buildscripts adds line items to your Mantid.user.properties file, whilst doing so it limits your core count and turns off all the network-based items. This is problematic for development as your algorithms run slower (terrible for benchmarking), and phone home operations are turned off including update instruments.

If any of these settings are already set then copy, and replace them after scripts are done.

If done before buildscript is removed from buildconfig/Jenkins then please also add support for the none-conda older dependency management based scripts as well.