test: use explicit p2p objects where available

To make the intent of the tests easier to understand, we reference the
p2p connection objects by their explicit names instead of the p2ps array.

Author: guggero

test/functional/p2p_getdata.py

@@ -42,7 +42,7 @@ def run_test(self):
         good_getdata = msg_getdata()
         good_getdata.inv.append(CInv(t=2, h=best_block))
         p2p_block_store.send_and_ping(good_getdata)
-        p2p_block_store.wait_until(lambda: self.nodes[0].p2ps[0].blocks[best_block] == 1)
+        p2p_block_store.wait_until(lambda: p2p_block_store.blocks[best_block] == 1)
 
 
 if __name__ == '__main__':

test/functional/wallet_resendwallettransactions.py

@@ -58,7 +58,7 @@ def run_test(self):
         two_min = 2 * 60
         node.setmocktime(now + twelve_hrs - two_min)
         time.sleep(2) # ensure enough time has passed for rebroadcast attempt to occur
-        assert_equal(int(txid, 16) in node.p2ps[1].get_invs(), False)
+        assert_equal(int(txid, 16) in peer_second.get_invs(), False)
 
         self.log.info("Bump time & check that transaction is rebroadcast")
         # Transaction should be rebroadcast approximately 24 hours in the future,