Fix corefx x86 testing and small netci.groovy fixes

Fix corefx x86 testing and small netci.groovy fixes

run-corefx-tests.py fixes
- Switch to using the same corefx build switches as the corefx CI.

netci.groovy fixes
- Add COMPlus_Ready2Run=0 to existing ZapDisable jobs to get the coverage
  we intended to have in these jobs.  Previously, R2R images were slipping
  through.

- Add architecture to the trigger strings fore corefx jobs so it's
  possible to request x86 corefx runs.

- Add the -u option to python command line in netci.groovy so Python
  output is synchronized with subcommand output in the CI logs.

- Fix whitespace in name formatting of corefx_baseline jobs

- Remove trailing (sorry, my editor did this and now it is too hard to
  undo.  Add ?w=1 to Github diff URL to filter out ws diffs.)

Commit migrated from https://github.com/dotnet/coreclr/commit/9ce6f601426c86d48c1c8a78b3558c7456caa719