c-ares:  Add debugging printfs for ENOMEM cases.

And clean up some whitespace indentation around
where code was changed.

Signed-off-by: Ben Greear <greearb@candelatech.com>
c-ares:  Add error code for no-servers-configured.

Also, set nservers to -2 on destroy, so we can tell if
nservers is < 0 because it was never properly initialized,
or if it was instead cleared by user for some reason.

Signed-off-by: Ben Greear <greearb@candelatech.com>