Fix memory leak in ecdsa_test.

This one really needs to get C++'d.

Change-Id: I088f3b77867af0cfc2da8324ba87954ef4cbba74
Reviewed-on: https://boringssl-review.googlesource.com/4350
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/crypto/ecdsa/ecdsa_test.c b/crypto/ecdsa/ecdsa_test.c
index 16b474d..12d02d6 100644
--- a/crypto/ecdsa/ecdsa_test.c
+++ b/crypto/ecdsa/ecdsa_test.c
@@ -313,6 +313,8 @@
     }
     fprintf(out, ".");
     fflush(out);
+    ECDSA_SIG_free(ecdsa_sig);
+    ecdsa_sig = NULL;
     OPENSSL_free(signature);
     signature = NULL;