Add unittest for All/AnyDiskOfType
Add unittest for All/AnyDiskOfType

The functions are pure and it's a shame they aren't already tested
thoroughly.

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

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