monitor: Clean up around monitor_handle_fd_param()

monitor: Clean up around monitor_handle_fd_param()

monitor_handle_fd_param() is a wrapper around
monitor_handle_fd_param2() that feeds errors to qerror_report_err()
instead of returning them.  qerror_report_err() is inappropriate in
many contexts.  monitor_handle_fd_param() looks simpler than
monitor_handle_fd_param2(), which tempts use.  Remove the temptation:
drop the wrapper and open-code the (trivial) error handling instead.

Replace the open-coded qerror_report_err() by error_report_err() in
places that already use error_report().  Turns out that's everywhere.

While there, rename monitor_handle_fd_param2() to monitor_fd_param().

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>