Bug description

When requesting the web wallet to sign a transaction, there is a chain parameter to specify the network like iota:mainnet. This should be used to do the dry run in the correct network, right now it's ignored and always uses the network selected in the wallet itself

Steps To reproduce the bug

1. call signTransaction() with the chain parameter set to a different network than what's selected in the browser wallet
2. dry run fails

Expected behaviour

Wallet should do the dry run with the node for the corresponding chain parameter and then the dry run should not fail

Actual behaviour

Dry run fails