Parachains can take a long time to initialize if relay chain sync service is busy

[tomaka]

The runtime service calls this line to initialize.

This has the effect of queuing a message on the channel from the sync service frontend to backend.
Unfortunately, if the backend is busy verifying things such as warp sync fragments, it will not process the messages in this channel, leading to the call to is_near_head_of_chain_heuristic not being answered until the verifications finish.