Updated libprocess tests for recent stout change.
Updated libprocess tests for recent stout change.

Specifically, commit bca95cabbfb07cc6293bf499f566244ea3bb0a94 resulted
in stout/tests/environment.hpp no longer including some headers and
defining some `using` aliases.

dforsyth/mesos,dforsyth/mesos,dforsyth/mesos,neilconway/mesos,chhsia0/mesos,kaysoky/mesos,kaysoky/mesos,zmalik/mesos,andschwa/mesos,neilconway/mesos,verizonlabs/mesos,neilconway/mesos,neilconway/mesos,andschwa/mesos,neilconway/mesos,abudnik/mesos,kaysoky/mesos,verizonlabs/mesos,kaysoky/mesos,Gilbert88/mesos,gsantovena/mesos,abudnik/mesos,reneploetz/mesos,abudnik/mesos,neilconway/mesos,reneploetz/mesos,zmalik/mesos,andschwa/mesos,zmalik/mesos,dforsyth/mesos,abudnik/mesos,asamerh4/mesos,andschwa/mesos,gsantovena/mesos,chhsia0/mesos,Gilbert88/mesos,verizonlabs/mesos,gsantovena/mesos,andschwa/mesos,verizonlabs/mesos,Gilbert88/mesos,jpeach/mesos,kaysoky/mesos,verizonlabs/mesos,reneploetz/mesos,zmalik/mesos,asamerh4/mesos,reneploetz/mesos,asamerh4/mesos,asamerh4/mesos,andschwa/mesos,reneploetz/mesos,verizonlabs/mesos,jpeach/mesos,chhsia0/mesos,asamerh4/mesos,abudnik/mesos,chhsia0/mesos,Gilbert88/mesos,reneploetz/mesos,dforsyth/mesos,asamerh4/mesos,gsantovena/mesos,jpeach/mesos,dforsyth/mesos,jpeach/mesos,Gilbert88/mesos,jpeach/mesos,chhsia0/mesos,asamerh4/mesos,chhsia0/mesos,neilconway/mesos,jpeach/mesos,zmalik/mesos,gsantovena/mesos,gsantovena/mesos,kaysoky/mesos,abudnik/mesos,verizonlabs/mesos,Gilbert88/mesos,gsantovena/mesos,zmalik/mesos,zmalik/mesos,chhsia0/mesos,jpeach/mesos,dforsyth/mesos,kaysoky/mesos,abudnik/mesos,reneploetz/mesos,Gilbert88/mesos,andschwa/mesos