Streamline some test setup.

Review Request #2167 - Created May 6, 2015 and submitted

Benjy Weinberger
jsirois, patricklaw, zundel
- Handle bootstrap options properly: Previously we were using
  the 'real' bootstrap option values, as set in pants.ini or whatever.
  Now we set the bootstrap option values the same as any other option -
  by capturing the default values, and then overriding those with any options
  specified in the test being run. This improves test isolation, as tests
  will no longer have access to real values by default.

- Get rid of some weird logic around linking ivy support files.
  It's not necessary, since we link the entire ivy support directory anyway.

- Don't bring in every registered BUILD file symbol and every source_root in every
  JvmToolTask test. Each test now brings in just what it needs.

CI passes:

Eric Ayers
Eric Ayers
Benjy Weinberger
Eric Ayers
Eric Ayers
Benjy Weinberger
Review request changed

Status: Closed (submitted)

Change Summary:

Submitted as 31f737fbd0f6f3188115580a73404d2e4378fe5a.