unit test for import key command

The check for the number of arguments fail.  On 2.0.4 this works correctly, I suspect commit 8fbe39ac505a03249922d69061e8bc2b28d7152c.  On 2.0.4 however the command causes the daemon to core dump later on

Error parsing arguments key import command line key import -z <validzonename> -k <validckanumber> --repository <validrepo> --bits 1024 --algorithm 8 --keystate active --keytype ZSK --inception_time 2017-03-01-12:00:00

 The issue has now been fixed as for OPENDNSSEC-880, however a unit test is appropriate.