qa: repair the rpc-test harness so it can start a DragonX node at all

The integration suite has never run against DragonX. Six independent
defects stacked up, each only visible once the previous was fixed:

1. test_framework used python2 implicit relative imports
   ("from authproxy import ..."), removed in python3, so every test died
   at import. Made explicit relative imports.

2. It wrote ZZZ.conf -- a Komodo assetchain convention -- while DragonX
   reads DRAGONX.conf. The daemon therefore never saw the generated
   config, fell back to mainnet defaults and tried to bind RPC 21769,
   which on a seed node is already held by the real node.

3. start_node() was hard-wired for the -ac_name=ZZZ assetchain tests: it
   took the RPC port from extra_args[3], passed extra_args[0] as argv[0]
   of the CLI, and only wrote a config when extra_args[0] matched. Any
   test that passes no extra args crashed on len(None). The generic path
   now takes the port from rpc_port(i) -- the same helper
   initialize_datadir() already used -- and drives the CLI with -datadir.

4. dragonxd refuses to start without an asmap file, which no test datadir
   had. initialize_datadir() now provisions one.

5. -asmap relative paths resolve against the NET-SPECIFIC datadir, so a
   copy in <datadir> is never found. Pass an absolute path.

6. Worst: -regtest was only ever set as "regtest=1" in the conf file,
   which DragonX ignores. Every "regtest" node therefore ran on MAINNET:
   real genesis, real seeds, real peers. An observed run synced 196,180
   live blocks and 679MB into /tmp before the test timed out. -regtest is
   now passed as a command-line flag, with -connect=0 so an isolated
   regtest node stays off the public network.

With these, nodes start, RPC answers, and tests run to a real result.
They do not all pass yet -- getblocktemplate.py reaches an assertion --
but that is now a test outcome rather than a harness failure.

qa/rpc-tests/test_framework/test_framework.py

@@ -11,8 +11,8 @@ import shutil
 import tempfile
 import traceback
 
-from authproxy import JSONRPCException
-from util import assert_equal, check_json_precision, \
+from .authproxy import JSONRPCException
+from .util import assert_equal, check_json_precision, \
     initialize_chain, initialize_chain_clean, \
     start_nodes, connect_nodes_bi, stop_nodes, \
     sync_blocks, sync_mempools, wait_bitcoinds
@@ -91,7 +91,7 @@ class BitcoinTestFramework(object):
         parser.add_option("--noshutdown", dest="noshutdown", default=False, action="store_true",
                           help="Don't stop nodes after the test execution")
         parser.add_option("--srcdir", dest="srcdir", default="../../src",
-                          help="Source directory containing hushd/hush-cli (default: %default)")
+                          help="Source directory containing dragonxd/dragonx-cli (default: %default)")
         parser.add_option("--tmpdir", dest="tmpdir", default=tempfile.mkdtemp(prefix="test"),
                           help="Root directory for datadirs")
         parser.add_option("--tracerpc", dest="trace_rpc", default=False, action="store_true",