crimson/osd: implicitly append '--smp 1' when invoked without it

crimson/osd: implicitly append '--smp 1' when invoked without it

This commit is basically a hack supposed to fulfil the obligation
of crimson being a drop-in replacement for the classical OSD
we already made by packaging it under `/usr/bin/ceph-osd`.
The discussion whether the interface-exactness should be continued
or not is out of scope of the commit; it's supposed just to handle
the issue unveiled by the Rook integration effort: `crimson-osd`
is unable to `--mkfs` because Seastar, if not restricted by passing
`--smp N`, considers all CPU cores available in the system when
allocating resources. This leads to the following error:

```
ERROR 2021-08-24 14:17:32,105 [shard 5] seastar - Could not setup Async I/O: Resource temporarily unavailable. The most common cause is not enough request capacity in /proc/sys/fs/aio-max-nr. Try increasing that number or reducing the amount of logical CPUs available for your application
```

This hack will need to be dropped when integrating multi-reactor
support in crimson.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>