Fix memory leaks for RSA key setters (#949)

Originally discussed in #940.

src/iperf_auth.c

@@ -172,6 +172,7 @@ EVP_PKEY *load_pubkey_from_base64(const char *buffer) {
     BIO* bio = BIO_new(BIO_s_mem());
     BIO_write(bio, key, key_len);
     EVP_PKEY *pkey = PEM_read_bio_PUBKEY(bio, NULL, NULL, NULL);
+    BIO_free(bio);
     return (pkey);
 }
 
@@ -196,6 +197,7 @@ EVP_PKEY *load_privkey_from_base64(const char *buffer) {
     BIO* bio = BIO_new(BIO_s_mem());
     BIO_write(bio, key, key_len);
     EVP_PKEY *pkey = PEM_read_bio_PrivateKey(bio, NULL, NULL, NULL);
+    BIO_free(bio);
     return (pkey);
 }