Windows: Enabled rest of `ProcessTest` suite.
Windows: Enabled rest of `ProcessTest` suite.

Several of these worked as-is, and the two firewall tests were fixed
by replace `path::join` (which joined with `\`) with
`strings::join("/")`.

Review: https://reviews.apache.org/r/67980

dforsyth/mesos,jpeach/mesos,reneploetz/mesos,jpeach/mesos,Gilbert88/mesos,chhsia0/mesos,Gilbert88/mesos,Gilbert88/mesos,chhsia0/mesos,kaysoky/mesos,jpeach/mesos,reneploetz/mesos,kaysoky/mesos,kaysoky/mesos,dforsyth/mesos,abudnik/mesos,gsantovena/mesos,gsantovena/mesos,Gilbert88/mesos,abudnik/mesos,chhsia0/mesos,abudnik/mesos,reneploetz/mesos,andschwa/mesos,Gilbert88/mesos,andschwa/mesos,abudnik/mesos,kaysoky/mesos,kaysoky/mesos,reneploetz/mesos,gsantovena/mesos,gsantovena/mesos,chhsia0/mesos,reneploetz/mesos,jpeach/mesos,gsantovena/mesos,chhsia0/mesos,chhsia0/mesos,abudnik/mesos,andschwa/mesos,dforsyth/mesos,reneploetz/mesos,reneploetz/mesos,dforsyth/mesos,jpeach/mesos,kaysoky/mesos,andschwa/mesos,kaysoky/mesos,chhsia0/mesos,dforsyth/mesos,Gilbert88/mesos,gsantovena/mesos,gsantovena/mesos,jpeach/mesos,dforsyth/mesos,andschwa/mesos,andschwa/mesos,abudnik/mesos,abudnik/mesos,Gilbert88/mesos,andschwa/mesos,dforsyth/mesos,jpeach/mesos