Add a generic mechanism to override mp?_wait_command's timeout behavior, which continues to invoke reinit by default. Invokers who set cm_timeout_handler may avoid automatic reinit and do their own handling. Adapt mp?sas_get_sata_identify to this mechanism and remove its callout hack. Reviewed by: scottl Sponsored by: Dell EMC Isilon Differential Revision: https://reviews.freebsd.org/D18614