Revert "Revert "tomd: Host Allocator should have readonly hosts property, which must me non-empty at instantiation""

This reverts commit 405d646aa583cda14b00056dc073eed4a89bfbc5.
Revert "tomd: improve output (both logging and failure messages) during host allocation process"

This reverts commit e7c90963a22a4978e89dee2ba3f8a98d580b6cb7.