wallet: Remove path checking code from loadwallet RPC

This commit does not change behavior except for error messages which now
include more complete information.

test/functional/rpc_createmultisig.py

@@ -129,7 +129,8 @@ class RpcCreateMultiSigTest(BitcoinTestFramework):
             try:
                 node1.loadwallet('wmulti')
             except JSONRPCException as e:
-                if e.error['code'] == -18 and 'Wallet wmulti not found' in e.error['message']:
+                path = os.path.join(self.options.tmpdir, "node1", "regtest", "wallets", "wmulti")
+                if e.error['code'] == -18 and "Wallet file verification failed. Failed to load database path '{}'. Path does not exist.".format(path) in e.error['message']:
                     node1.createwallet(wallet_name='wmulti', disable_private_keys=True)
                 else:
                     raise