Fix errors in AEAD test function

It was failing to set the key in the ENCRYPT direction before encrypting.
This just happened to work for GCM and CCM.

After re-encrypting, compare the length to the expected ciphertext
length not the plaintext length. Again this just happens to work for
GCM and CCM since they do not perform any kind of padding.
diff --git a/tests/suites/test_suite_cipher.function b/tests/suites/test_suite_cipher.function
index a7d3a6e..9a0637e 100644
--- a/tests/suites/test_suite_cipher.function
+++ b/tests/suites/test_suite_cipher.function
@@ -1011,6 +1011,9 @@
     TEST_ASSERT( memcmp( output, clear->x, clear->len ) == 0 );
 
     /* then encrypt the clear->x and make sure we get the same ciphertext and tag->x */
+    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key->x, 8 * key->len,
+                                             MBEDTLS_ENCRYPT ) );
+
     memset( output, 0xFF, sizeof( output ) );
     outlen = 0;
 
@@ -1023,7 +1026,7 @@
                                output_tag, tag->len );
     TEST_ASSERT( ret == 0 );
 
-    TEST_ASSERT( outlen == clear->len );
+    TEST_ASSERT( outlen == cipher->len );
     TEST_ASSERT( memcmp( output, cipher->x, cipher->len ) == 0 );
     TEST_ASSERT( memcmp( output_tag, tag->x, tag->len ) == 0 );