Upgrade select alpn callback

nghttp2 has added a new callback[1] which solves the issue we were
seeing previously with const.  This cleans up some NOLINT markers, but
should have no functional changes

[1] https://nghttp2.org/documentation/nghttp2_select_alpn.html#c.nghttp2_select_alpn

Tested:

Curl shows HTTP2 upgrade works properly.

* ALPN, offering h2
* ALPN, offering http/1.1
* ALPN, server accepted to use h2
* Using HTTP2, server supports multiplexing
* Connection state changed (HTTP/2 confirmed)

Change-Id: Ic41754c58e6166aac22ed5afca5371661db959da
Signed-off-by: Ed Tanous <etanous@nvidia.com>
diff --git a/src/ssl_key_handler.cpp b/src/ssl_key_handler.cpp
index 4423508..1d4039c 100644
--- a/src/ssl_key_handler.cpp
+++ b/src/ssl_key_handler.cpp
@@ -459,18 +459,15 @@
                                    const unsigned char* in, unsigned int inlen,
                                    void* /*unused*/)
 {
-    // There's a mismatch in constness for nghttp2_select_next_protocol.  The
-    // examples in nghttp2 don't show this problem.  Unclear what the right fix
-    // is here.
-
-    // NOLINTNEXTLINE(cppcoreguidelines-pro-type-const-cast)
-    unsigned char** outNew = const_cast<unsigned char**>(out);
-    int rv = nghttp2_select_next_protocol(outNew, outlen, in, inlen);
-    if (rv != 1)
+    int rv = nghttp2_select_alpn(out, outlen, in, inlen);
+    if (rv == -1)
     {
         return SSL_TLSEXT_ERR_NOACK;
     }
-
+    if (rv == 1)
+    {
+        BMCWEB_LOG_DEBUG("Selected HTTP2");
+    }
     return SSL_TLSEXT_ERR_OK;
 }