block/rbd: add all the currently supported runtime_opts

This adds all the currently supported runtime opts, which
are the options as parsed from the filename.  All of these
options are explicitly checked for during during runtime,
with an exception to the "keyvalue-pairs" option.

This option contains all the key/value pairs that the QEMU rbd
driver merely unescapes, and passes along blindly to rados.  This
option is a "legacy" option, and will not be exposed in the QAPI
or available for introspection.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>
