Revert "rgw: plain format always appends eol to data"

This commit breaks the swift unit test. The reason is that it
makes it so that returned error status ends with eol, which
is not as expected.

This reverts commit c31aff5f9f0b9fe4ada6b259dd1f424627b3e875.

Signed-off-by: Yehuda Sadeh <yehuda@inktank.com>