MDEV-9836 Connection lost when using SSL

Don't read from socket in yassl in SSL_pending().
Just return size of the buffered processed data.
This is what OpenSSL is documented to do too:

  SSL_pending() returns the number of bytes which have been processed,
  buffered and are available inside ssl for immediate read.

extra/yassl/src/ssl.cpp

@@ -1471,10 +1471,6 @@ int SSL_peek(SSL* ssl, void* buffer, int sz)
 
 int SSL_pending(SSL* ssl)
 {
-    // Just in case there's pending data that hasn't been processed yet...
-    char c;
-    SSL_peek(ssl, &c, 1);
-    
     return ssl->bufferedData();
 }
 

mysql-test/r/ssl_timeout-9836.result

@@ -0,0 +1,7 @@
+SET @@net_read_timeout=1;
+SELECT 1;
+1
+1
+SELECT 1;
+1
+1

mysql-test/t/ssl_timeout-9836.opt

@@ -0,0 +1 @@
+--loose-thread-handling=pool-of-threads

mysql-test/t/ssl_timeout-9836.test

@@ -0,0 +1,11 @@
+#
+# MDEV-9836 Connection lost when using SSL
+#
+-- source include/have_ssl_communication.inc
+connect(con1,localhost,root,,,,,SSL);
+SET @@net_read_timeout=1;
+SELECT 1;
+# MDEV-9836 - YASSL bug - SSL connection lost if it has been idle, for longer than net_read_timeout
+-- sleep 2
+SELECT 1;
+disconnect con1;