test: don't run old binaries under valgrind

This is unnecessary and caused test failures. The backward
compatibility tests are meant to find regressions in the
current codebase, not to detect bugs in older releases.

test/functional/test_framework/test_framework.py

@@ -185,7 +185,7 @@ class BitcoinTestFramework(metaclass=BitcoinTestMetaClass):
         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. Does not apply to previous release binaries.")
         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, help="adjust test timeouts by a factor. Setting it to 0 disables all timeouts")

test/functional/test_framework/test_node.py

@@ -110,7 +110,8 @@ class TestNode():
         if self.descriptors is None:
             self.args.append("-disablewallet")
 
-        if use_valgrind:
+        # Use valgrind, expect for previous release binaries
+        if use_valgrind and version is None:
             default_suppressions_file = Path(__file__).parents[3] / "contrib" / "valgrind.supp"
             suppressions_file = os.getenv("VALGRIND_SUPPRESSIONS_FILE",
                                           default_suppressions_file)