test --coverage: Shut down live-server gracefully
test --coverage: Shut down live-server gracefully

`./go test --coverage` serves results via live-server when
`COVERAGE_REPORT_SERVER='true'`. Previously, the script would exit with
a signal status when the user would enter CTRL-C to terminate the
server, regardless of whether the test suite actually passed or failed.

`./go test --coverage` now exits with the correct status when the user
terminates the server. It also emits informational messages when
live-server is started and terminated.

mbland/url-pointers,mbland/custom-links,mbland/custom-links,mbland/custom-links,mbland/url-pointers,mbland/url-pointers