[reclass] dbs, msg: Inherit only infra classes

[reclass] dbs, msg: Inherit only infra classes

All other VCP nodes (mdb, prx, ctl etc.) inherit only the infra
subdir of each scenario, so apply the same to dbs, msg.

This should cut down some operations during reclass interpolation
for affected nodes, without any changes in output pillar data.

Change-Id: I77ae6e1d5658cba87fcd8c45a5f8f5e177e0eda9
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>