Cleanup the default build manager on new TestEnvironment instances
Cleanup the default build manager on new TestEnvironment instances

To ensure that prior tests do not influence the current test using the TestEnvironmet

chipitsine/msbuild,rainersigwald/msbuild,cdmihai/msbuild,mono/msbuild,Microsoft/msbuild,cdmihai/msbuild,AndyGerlicher/msbuild,mono/msbuild,Microsoft/msbuild,Microsoft/msbuild,rainersigwald/msbuild,mono/msbuild,Microsoft/msbuild,sean-gilliam/msbuild,cdmihai/msbuild,sean-gilliam/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,jeffkl/msbuild,rainersigwald/msbuild,chipitsine/msbuild,rainersigwald/msbuild,AndyGerlicher/msbuild,sean-gilliam/msbuild,mono/msbuild,jeffkl/msbuild,chipitsine/msbuild,jeffkl/msbuild,cdmihai/msbuild,AndyGerlicher/msbuild,chipitsine/msbuild,jeffkl/msbuild