vtls: compare and clone ssl configs properly

Compare these settings in Curl_ssl_config_matches():
- verifystatus (CURLOPT_SSL_VERIFYSTATUS)
- random_file (CURLOPT_RANDOM_FILE)
- egdsocket (CURLOPT_EGDSOCKET)

Also copy the setting "verifystatus" in Curl_clone_primary_ssl_config(),
and copy the setting "sessionid" unconditionally.

This means that reusing connections that are secured with a client
certificate is now possible, and the statement "TLS session resumption
is disabled when a client certificate is used" in the old advisory at
https://curl.haxx.se/docs/adv_20170419.html is obsolete.

Reviewed-by: Daniel Stenberg

Closes #1917

lib/urldata.h

@@ -210,13 +210,13 @@ struct ssl_primary_config {
   bool verifypeer;       /* set TRUE if this is desired */
   bool verifyhost;       /* set TRUE if CN/SAN must match hostname */
   bool verifystatus;     /* set TRUE if certificate status must be checked */
+  bool sessionid;        /* cache session IDs or not */
   char *CApath;          /* certificate dir (doesn't work on windows) */
   char *CAfile;          /* certificate to verify peer against */
   char *clientcert;
   char *random_file;     /* path to file containing "random" data */
   char *egdsocket;       /* path to file containing the EGD daemon socket */
   char *cipher_list;     /* list of ciphers to use */
-  bool sessionid;        /* cache session IDs or not */
 };
 
 struct ssl_config_data {