SSL: handled long string truncation in ngx_ssl_error().

If no space left in buffer after adding formatting symbols, error message
could be left without terminating null.  The fix is to output message using
actual length.

src/event/ngx_event_openssl.c

diff --git a/src/event/ngx_event_openssl.c b/src/event/ngx_event_openssl.c
index e9edf31..8550da9 100644
--- a/src/event/ngx_event_openssl.c
+++ b/src/event/ngx_event_openssl.c
@@ -2045,7 +2045,7 @@
         (void) ERR_get_error();
     }
 
-    ngx_log_error(level, log, err, "%s)", errstr);
+    ngx_log_error(level, log, err, "%*s)", p - errstr, errstr);
 }