Merge bitcoin#23516: test: Force --nosandbox when --valgrind

fa9c26a test: Force --nosandbox when --valgrind (MarcoFalke)

Pull request description:

  The two options are mutually exclusive and will result in a test failure. Fix that.

  Can be tested with:

  ```
  $ ./test/functional/wallet_disable.py --valgrind

ACKs for top commit:
  fanquake:
    ACK fa9c26a

Tree-SHA512: 7d1c36c1b6627ca041757eb0515a0d6cc962a56d783ee4f5647a2ddc2d104491f0586a8ea0b8acebe0a203190f4f5567b349123dfd4c181bcc63361174a8ab63

test/functional/test_framework/test_framework.py

@@ -101,7 +101,7 @@ def __init__(self):
         self.supports_cli = True
         self.bind_to_localhost_only = True
         self.parse_args()
-        self.disable_syscall_sandbox = self.options.nosandbox
+        self.disable_syscall_sandbox = self.options.nosandbox or self.options.valgrind
         self.default_wallet_name = "default_wallet" if self.options.descriptors else ""
         self.wallet_data_filename = "wallet.dat"
         # Optional list of wallet names that can be set in set_test_params to
@@ -188,7 +188,7 @@ def parse_args(self):
         parser.add_argument("--perf", dest="perf", default=False, action="store_true",
                             help="profile running nodes with perf for the duration of the test")
         parser.add_argument("--valgrind", dest="valgrind", default=False, action="store_true",
-                            help="run nodes under the valgrind memory error detector: expect at least a ~10x slowdown, valgrind 3.14 or later required")
+                            help="run nodes under the valgrind memory error detector: expect at least a ~10x slowdown. valgrind 3.14 or later required. Forces --nosandbox.")
         parser.add_argument("--randomseed", type=int,
                             help="set a random seed for deterministically reproducing a previous test run")
         parser.add_argument('--timeout-factor', dest="timeout_factor", type=float, default=1.0, help='adjust test timeouts by a factor. Setting it to 0 disables all timeouts')