[ICS02] ClientStatePath is not checked during client creation

[Farhad-Shabani]

Problem Statment

• The ICS02 specifies that for handling a client creation request, the process should check if the submitted ClientState already exists in the ClientStatePath!

  abortTransactionUnless(provableStore.get(clientStatePath(identifier)) === null)

• Note that an incorrect use of SetClientState can result in a ClientState being set to the same store as the one that is going to be set by a MsgCreateClient.

In IBC-go

• There is a GetClientState method, but not used to perform this check. Instead they create an isolated store by StoreClient for this purpose.
• This can't be applied to IBC-rs, as we do not access to the store.

Acceptance Criteria

Check ClientStatePath to ensure the received ClientState via a MsgCreateClient does not exist