test: fix messages and use return to skip tests

This is a followup of https://github.com/nodejs/io.js/pull/2109.
The tests which didn't make it in #2109, are included in this patch.
The skip messages are supposed to follow the format

    1..0 # Skipped: [Actual reason why the test is skipped]

and the tests should be skipped with the return statement.

PR-URL: https://github.com/nodejs/io.js/pull/2290


Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>