Assemble: check inargv before complaining about stray arguments.

Assemble: check inargv before complaining about stray arguments.

If --assemble is given a container and some other devices to assemble
an array from, it complains with an error because that doesn't make
sense.
However it currently also complains if the list of devices was extract
from the config file rather than being given on the command line.
That is not appropriate.

So add an '&& inargv' test to ensure that we are really complaining
about the right thing.

Signed-off-by: NeilBrown <neilb@suse.de>
Acked-by: Dan Williams <dan.j.williams@intel.com>