Fix import-rescan.py and add workaround for pruning mode

Added a workaround to the masternode+pruning mode check to allow pruning
in regtest. The actual bug behind the masternode+pruning check is not
touched this way. Please read the linked GitHub issues for details.

qa/rpc-tests/import-rescan.py

@@ -112,7 +112,8 @@ class ImportRescanTest(BitcoinTestFramework):
         extra_args = [["-debug=1"] for _ in range(self.num_nodes)]
         for i, import_node in enumerate(IMPORT_NODES, 1):
             if import_node.prune:
-                extra_args[i] += ["-prune=1"]
+                # txindex is enabled by default in Dash and needs to be disabled for import-rescan.py
+                extra_args[i] += ["-prune=1", "-txindex=0", "-reindex-chainstate"]
 
         self.nodes = start_nodes(self.num_nodes, self.options.tmpdir, extra_args)
         for i in range(1, self.num_nodes):

src/init.cpp

@@ -1745,7 +1745,8 @@ bool AppInitMain(boost::thread_group& threadGroup, CScheduler& scheduler)
     fMasternodeMode = GetBoolArg("-masternode", false);
     // TODO: masternode should have no wallet
 
-    if((fMasternodeMode || masternodeConfig.getCount() > -1) && fTxIndex == false) {
+    if((fMasternodeMode || masternodeConfig.getCount() > -1) && fTxIndex == false
+       && chainparams.NetworkIDString() != CBaseChainParams::REGTEST) { // TODO remove this when pruning is fixed. See https://github.com/dashpay/dash/pull/1817 and https://github.com/dashpay/dash/pull/1743
         return InitError("Enabling Masternode support requires turning on transaction indexing."
                   "Please add txindex=1 to your configuration and start with -reindex");
     }