[tests] Fix quoting issue for a ToolTask test on Unix
[tests] Fix quoting issue for a ToolTask test on Unix

Fixes ErrorWhenTextSentToStandardError and
DoNotErrorWhenTextSentToStandardError.

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