server,tests: explicitly disable DRPC setting if option is TestDRPCDisabled

This change ensures a clear distinction between an unset DRPC option and an
explicitly disabled one. If the DRPC option is unset at both the test and
package levels, we will not modify the setting. This allows the system to
use the default value of `ExperimentalDRPCEnabled`, which can be overridden
for development via `COCKROACH_EXPERIMENTAL_DRPC_ENABLED`. When the option
is explicitly set to `TestDRPCDisabled`, we will now explicitly disable the
setting.

Release note: none
Epic: none

Author: shubhamdhama

pkg/server/testserver.go

@@ -333,8 +333,11 @@ func makeTestConfigFromParams(params base.TestServerArgs) Config {
 		cfg.TestingKnobs.AdmissionControlOptions = &admission.Options{}
 	}
 
-	if params.DefaultDRPCOption == base.TestDRPCEnabled {
+	switch params.DefaultDRPCOption {
+	case base.TestDRPCEnabled:
 		rpcbase.ExperimentalDRPCEnabled.Override(context.Background(), &st.SV, true)
+	case base.TestDRPCDisabled:
+		rpcbase.ExperimentalDRPCEnabled.Override(context.Background(), &st.SV, false)
 	}
 
 	return cfg

pkg/testutils/serverutils/test_server_shim.go

@@ -555,6 +555,8 @@ func ShouldEnableDRPC(
 	case base.TestDRPCEnabledRandomly:
 		rng, _ := randutil.NewTestRand()
 		enableDRPC = rng.Intn(2) == 0
+	case base.TestDRPCUnset:
+		return base.TestDRPCUnset
 	}
 
 	if enableDRPC {