API: libcrmcommon: Map pcmk_rc_no_output to CRM_EX_OK

Previously it was mapped to CRM_EX_IOERR. However, it's often (most
often?) used in non-error situations. Two examples:

• An internal output object (pcmk__output_t) is in quiet mode.
• There's no relevant data to output.

Signed-off-by: Reid Wahl <nrwahl@protonmail.com>