CLEANUP: ssl: use realloc() instead of free()+malloc()

There was a free(ptr) followed by ptr=malloc(ptr, len), which is the
equivalent of ptr = realloc(ptr, len) but slower and less clean. Let's
replace this.
diff --git a/src/ssl_sock.c b/src/ssl_sock.c
index b10281a..2abd666 100644
--- a/src/ssl_sock.c
+++ b/src/ssl_sock.c
@@ -3996,8 +3996,8 @@
 		if (s->ssl_ctx.reused_sess[tid].ptr && s->ssl_ctx.reused_sess[tid].allocated_size >= len) {
 			ptr = s->ssl_ctx.reused_sess[tid].ptr;
 		} else {
-			free(s->ssl_ctx.reused_sess[tid].ptr);
-			ptr = s->ssl_ctx.reused_sess[tid].ptr = malloc(len);
+			ptr = realloc(s->ssl_ctx.reused_sess[tid].ptr, len);
+			s->ssl_ctx.reused_sess[tid].ptr = ptr;
 			s->ssl_ctx.reused_sess[tid].allocated_size = len;
 		}
 		if (s->ssl_ctx.reused_sess[tid].ptr) {