Fix punctuation in gorouter spec descriptions

- (just an excuse to modify a job)

[#71479974]

Signed-off-by: David Varvel <dvarvel@pivotallabs.com>
Revert "Remove unused libyaml package"

libyaml must exist due to a bug in bosh https://www.pivotaltracker.com/story/show/71524826

This reverts commit a7643f0adc51940a27e75a44a61d3678cbdae329.