remove redundant requests for "earliest" block when forking

[MicaiahReid]

With the introduction of #3755, we now make two requests for the earliest block from the remote when forking. One is to set up the persistent cache, and the other is to set up the earliest tag in the block manager.

This should only happen the first time you run ganache with forking. After that the persistent cache should have that request saved. But still, it's less than ideal.