Fix printSolutionLine to handle non-DRBD steps

Currently Cluster.printSolutionLine function always wants to print the
old and new secondary, and as such it fails (ugly) for moves of
non-DRBD instances. Change it so that it looks explicitly for
noSecondary nodes, and format the output different in that case.

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>