[tests] Speed up rpc_fundrawtransaction.py

Most of the time in rpc_fundrawtransaction.py is spent waiting for
unconfirmed transactions to propagate. Net processing adds a poisson
random delay to the time it will INV transactions with a mean interval
of 5 seconds. Calls like the following:

```
self.nodes[2].sendrawtransaction(signedTx['hex'])
self.sync_all()
self.nodes[1].generate(1)
````

will therefore introduce a delay waiting for the mempools to sync.
Instead just generate the block on the node that sent the transaction:

```
self.nodes[2].sendrawtransaction(signedTx['hex'])
self.nodes[2].generate(1)
```

rpc_fundrawtransaction.py is not intended to be a test for transaction
relay, so it's ok to do this.

test/functional/rpc_fundrawtransaction.py

@@ -470,8 +470,7 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         # Send 1.2 BTC to msig addr.
         self.nodes[0].sendtoaddress(mSigObj, 1.2)
-        self.sync_all()
-        self.nodes[1].generate(1)
+        self.nodes[0].generate(1)
         self.sync_all()
 
         oldBalance = self.nodes[1].getbalance()
@@ -482,8 +481,7 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         signedTx = self.nodes[2].signrawtransactionwithwallet(fundedTx['hex'])
         self.nodes[2].sendrawtransaction(signedTx['hex'])
-        self.sync_all()
-        self.nodes[1].generate(1)
+        self.nodes[2].generate(1)
         self.sync_all()
 
         # Make sure funds are received at node1.
@@ -550,8 +548,7 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         # Empty node1, send some small coins from node0 to node1.
         self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), self.nodes[1].getbalance(), "", "", True)
-        self.sync_all()
-        self.nodes[0].generate(1)
+        self.nodes[1].generate(1)
         self.sync_all()
 
         for i in range(0,20):
@@ -579,8 +576,7 @@ class RawTransactionsTest(BitcoinTestFramework):
 
         # Again, empty node1, send some small coins from node0 to node1.
         self.nodes[1].sendtoaddress(self.nodes[0].getnewaddress(), self.nodes[1].getbalance(), "", "", True)
-        self.sync_all()
-        self.nodes[0].generate(1)
+        self.nodes[1].generate(1)
         self.sync_all()
 
         for i in range(0,20):
@@ -597,8 +593,7 @@ class RawTransactionsTest(BitcoinTestFramework):
         fundedTx = self.nodes[1].fundrawtransaction(rawtx)
         fundedAndSignedTx = self.nodes[1].signrawtransactionwithwallet(fundedTx['hex'])
         self.nodes[1].sendrawtransaction(fundedAndSignedTx['hex'])
-        self.sync_all()
-        self.nodes[0].generate(1)
+        self.nodes[1].generate(1)
         self.sync_all()
         assert_equal(oldBalance+Decimal('50.19000000'), self.nodes[0].getbalance()) #0.19+block reward