Omit `cpage` query var in comment link if comment pagination is disabled.

WP 4.4 changed the way comment pagination is calculated. See #8071. In the
context of `get_comment_link()`, these changes introduced a regression that
causes `cpage` (or its pretty-permalink correlate `comment-page-x`) to appear
in comment links when comment pagination is disabled. The current changeset
fixes the regression.

Fixes #34946.
Built from https://develop.svn.wordpress.org/trunk@35933


git-svn-id: https://core.svn.wordpress.org/trunk@35897 1a063a9b-81f0-0310-95a4-ce76da25c4cd