Add test for replace_new_secondary
Add test for replace_new_secondary

Currently there is no test for the code path of
LUInstanceReplaceDisks for the replace_new_secondary option. This is
problematic, because it is currently being modified.

Signed-off-by: Aaron Karper <99cc1031546340b2b8ced5fe338b5890677a56ca@google.com>
Reviewed-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>

mbakke/ganeti,andir/ganeti,leshchevds/ganeti,mbakke/ganeti,onponomarev/ganeti,apyrgio/ganeti,leshchevds/ganeti,mbakke/ganeti,ganeti/ganeti,dimara/ganeti,yiannist/ganeti,andir/ganeti,bitemyapp/ganeti,grnet/snf-ganeti,leshchevds/ganeti,ganeti/ganeti,onponomarev/ganeti,ganeti/ganeti,grnet/snf-ganeti,andir/ganeti,yiannist/ganeti,yiannist/ganeti,apyrgio/ganeti,bitemyapp/ganeti,dimara/ganeti