Set \imprecise when a configuration is chosen

Set \imprecise when a configuration is chosen

Instead of setting \imprecise at the end of the loop if a configuration
was found (which clobbered valuable information, see dae2406187), set it
each time a new configuration is chosen.

In the second loop that tries harder, resetting \imprecise also avoids a
previous "imprecise->set(AUDIO, 0)" to last even if another
configuration is chosen later.

Last but not least, it will enable correctly setting the midi input
count hoped for by the configuration.