Prevent ChainingCredentialsProvider from adding delegated providers twice

Signed-off-by: Rüdiger Herrmann <ruediger.herrmann@gmx.de>
Change-Id: Icc0907af4fe26877d066db3c813dba37213a3ccc

org.eclipse.jgit/src/org/eclipse/jgit/transport/ChainingCredentialsProvider.java

@@ -70,8 +70,6 @@ public class ChainingCredentialsProvider extends CredentialsProvider {
 	public ChainingCredentialsProvider(CredentialsProvider... providers) {
 		this.credentialProviders = new ArrayList<CredentialsProvider>(
 				Arrays.asList(providers));
-		for (CredentialsProvider p : providers)
-			credentialProviders.add(p);
 	}
 
 	/**