files-reg: don't leak a file descriptor

CID 154850 (#1 of 1): Resource leak (RESOURCE_LEAK)
9. leaked_handle: Handle variable cwd_fd going out of scope leaks the handle.

Reported-by: coverity
Signed-off-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

files-reg.c

@@ -471,6 +471,7 @@ void try_clean_remaps(int ns_fd)
 
 		if (setns(ns_fd, CLONE_NEWNS) < 0) {
 			close(old_ns);
+			close(cwd_fd);
 			pr_perror("`- Can't switch");
 			return;
 		}