Fix: enable-consumer for all domains missing dir

So the fix here is to enable consumer for all domains if no domain is
given to the command line. This way, the session daemon can handle
correctly the trace directory path for the right domain.

Note that there is *no* switch for all domains (-a, --all) so omitting
the domain (-u or -k) automatically creates a UST and kernel session, if
none, and set the consumer for both of them. If one fails, the command
is stopped. All in all, to be sure, use a domain with the command ;).

Fixes #333

Signed-off-by: David Goulet <dgoulet@efficios.com>