Delegate crypto algorithm creation to InsecureCipherFactory

This is a preparation change to Bazel build implementation. Error
Prone rejects the code with variable crypto algorithm as insecure
see: [1].

[1] http://errorprone.info/bugpattern/InsecureCryptoUsage

Change-Id: I92db70a7da454bc364597a995e8be5dccc2d6427
Signed-off-by: David Ostrovsky <david@ostrovsky.org>

org.eclipse.jgit.test/tst/org/eclipse/jgit/transport/WalkEncryptionTest.java

@@ -91,7 +91,6 @@ import java.util.Set;
 import java.util.TreeSet;
 import java.util.UUID;
 
-import javax.crypto.Cipher;
 import javax.crypto.SecretKeyFactory;
 
 import org.eclipse.jgit.api.Git;
@@ -772,16 +771,16 @@ public class WalkEncryptionTest {
 			String profile = props.getProperty(AmazonS3.Keys.CRYPTO_ALG);
 			String version = props.getProperty(AmazonS3.Keys.CRYPTO_VER,
 					WalkEncryption.Vals.DEFAULT_VERS);
-			String crytoAlgo;
+			String cryptoAlgo;
 			String keyAlgo;
 			switch (version) {
 			case WalkEncryption.Vals.DEFAULT_VERS:
 			case WalkEncryption.JGitV1.VERSION:
-				crytoAlgo = profile;
+				cryptoAlgo = profile;
 				keyAlgo = profile;
 				break;
 			case WalkEncryption.JGitV2.VERSION:
-				crytoAlgo = props
+				cryptoAlgo = props
 						.getProperty(profile + WalkEncryption.Keys.X_ALGO);
 				keyAlgo = props
 						.getProperty(profile + WalkEncryption.Keys.X_KEY_ALGO);
@@ -790,7 +789,7 @@ public class WalkEncryptionTest {
 				return false;
 			}
 			try {
-				Cipher.getInstance(crytoAlgo);
+				InsecureCipherFactory.create(cryptoAlgo);
 				SecretKeyFactory.getInstance(keyAlgo);
 				return true;
 			} catch (Throwable e) {