zdtm: Don't modify global @errno in test_msg

This is logging routine, lets it not affect the global @errno.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

test/zdtm/lib/msg.c

@@ -39,6 +39,7 @@ void test_msg(const char *format, ...)
 	va_list arg;
 	int off = 0;
 	char buf[PAGE_SIZE];
+	int __errno = errno;
 	struct timeval tv;
 	struct tm *tm;
 
@@ -57,4 +58,5 @@ void test_msg(const char *format, ...)
 	va_end(arg);
 
 	fprintf(stderr, "%s", buf);
+	errno = __errno;
 }