[Fix] only reregister if flag is set

[camfairchild]

This PR fixes a bug where --wallet.reregister False was ignored during btcli run
The expected behaviour is to not reregister a wallet that is not registered, and instead exit.
The current behaviour is to start the registration, regardless, causing the bug.

This PR fixes the bug and adds a test to verify this.

This PR also fixes a bug with the cli factory where the args where supposed to be passed in to be parsed early in the function as well, see /bittensor/_config/__init__.py#73