Add TMaybeList as a new type for parameters
Add TMaybeList as a new type for parameters

This will be used as the type for the reason trail parameter.

Signed-off-by: Michele Tartara <05f7077a2c6cbbdc4af4ba42e3ef89a0df846179@google.com>
Reviewed-by: Helga Velroyen <2d0126b1ec6f9ec5cbec4a7012aa14faeaef10f5@google.com>

mbakke/ganeti,mbakke/ganeti,ganeti/ganeti,onponomarev/ganeti,andir/ganeti,andir/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,apyrgio/snf-ganeti,apyrgio/ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,grnet/snf-ganeti,leshchevds/ganeti,ganeti/ganeti,andir/ganeti,apyrgio/ganeti,leshchevds/ganeti,dimara/ganeti,bitemyapp/ganeti,dimara/ganeti,onponomarev/ganeti,grnet/snf-ganeti,mbakke/ganeti,yiannist/ganeti,ganeti/ganeti,leshchevds/ganeti,bitemyapp/ganeti,apyrgio/snf-ganeti