test: Add unit test coverage for Init and Shutdown code

Currently this code is not called in unit tests. Calling should make it
possible to write tests for things like IPC exceptions being thrown during
shutdown.

src/test/util/setup_common.cpp

@@ -115,6 +115,14 @@ BasicTestingSetup::BasicTestingSetup(const ChainType chainType, TestOpts opts)
     if (!EnableFuzzDeterminism()) {
         SeedRandomForTest(SeedRand::FIXED_SEED);
     }
+
+    // Reset globals
+    fDiscover = true;
+    fListen = true;
+    SetRPCWarmupStarting();
+    g_reachable_nets.Reset();
+    ClearLocal();
+
     m_node.shutdown_signal = &m_interrupt;
     m_node.shutdown_request = [this]{ return m_interrupt(); };
     m_node.args = &gArgs;
@@ -214,7 +222,10 @@ BasicTestingSetup::~BasicTestingSetup()
     } else {
         fs::remove_all(m_path_root);
     }
+    // Clear all arguments except for -datadir, which GUI tests currently rely
+    // on to be set even after the testing setup is destroyed.
     gArgs.ClearArgs();
+    gArgs.ForceSetArg("-datadir", fs::PathToString(m_path_root));
 }
 
 ChainTestingSetup::ChainTestingSetup(const ChainType chainType, TestOpts opts)