cephadm: return nonzero exit code when applying spec fails in bootstrap

cephadm: return nonzero exit code when applying spec fails in bootstrap

This is mostly useful for testing automation, but right now if applying the
spec provided with --apply-spec fails, the return code remains zero. We don't
want to error out entirely in that case as we still want to print the remaining
output (e.g. the dashboard password). Continuing onward and then returning a
nonzero code could provide a balance where we still give all the output but
still have something to make it easier for those writing automation around bootstrap.

Fixes: https://tracker.ceph.com/issues/57173
Signed-off-by: Adam King <adking@redhat.com>