Fix Door Lock cluster to not repond DUPLICATE when there is no duplication of credentials. (project-chip#39279)

Spec issue tracking the spec not being clear:
CHIP-Specifications/connectedhomeip-spec#11707

Cherry-pick of project-chip#39254

Author: bzbarsky-apple

src/app/clusters/door-lock-server/door-lock-server.cpp

@@ -710,6 +710,17 @@ void DoorLockServer::setCredentialCommandHandler(
     // appclusters, 5.2.4.41.1: we should return DUPLICATE in the response if we're trying to create duplicated credential entry
     for (uint16_t i = 1; CredentialTypeEnum::kProgrammingPIN != credentialType && (i <= maxNumberOfCredentials); ++i)
     {
+        // Ignore the slot we are trying to set, because setting a credential to
+        // the same value as it already has should be just fine.
+        //
+        // This is not clearly defined in the spec;
+        // https://github.com/CHIP-Specifications/connectedhomeip-spec/issues/11707
+        // tracks that.
+        if (i == credentialIndex)
+        {
+            continue;
+        }
+
         EmberAfPluginDoorLockCredentialInfo currentCredential;
         if (!emberAfPluginDoorLockGetCredential(commandPath.mEndpointId, i, credentialType, currentCredential))
         {

src/app/tests/suites/DL_UsersAndCredentials.yaml

@@ -1117,6 +1117,32 @@ tests:
               - name: "NextCredentialIndex"
                 value: null
 
+    - label: "Verify setting credential to same value is allowed"
+      command: "SetCredential"
+      timedInteractionTimeoutMs: 10000
+      arguments:
+          values:
+              - name: "OperationType"
+                value: 2 # Modify
+              - name: "Credential"
+                value: { CredentialType: 1, CredentialIndex: 1 }
+              - name: "CredentialData"
+                value: "000000"
+              - name: "UserIndex"
+                value: 1
+              - name: "UserStatus"
+                value: null
+              - name: "UserType"
+                value: null
+      response:
+          values:
+              - name: "Status"
+                value: 0x00
+              - name: "UserIndex"
+                value: null
+              - name: "NextCredentialIndex"
+                value: 2
+
     - label: "Create new PIN credential and user with index 0 fails"
       command: "SetCredential"
       timedInteractionTimeoutMs: 10000