network_manager_main: errno is not negative

This looks like it got copied from somewhere. Don't negate the errno,
just return it as-is.

Tested:
    Compiled as expected.

Change-Id: I6b28030bf211d12bacab6b69191406e612a6e45f
Signed-off-by: William A. Kennington III <wak@google.com>
diff --git a/network_manager_main.cpp b/network_manager_main.cpp
index 616d37e..2bc203f 100644
--- a/network_manager_main.cpp
+++ b/network_manager_main.cpp
@@ -66,9 +66,8 @@
     auto fd = socket(PF_NETLINK, SOCK_RAW | SOCK_NONBLOCK, NETLINK_ROUTE);
     if (fd < 0)
     {
-        auto r = -errno;
         log<level::ERR>("Unable to create the net link socket",
-                        entry("ERRNO=%d", r));
+                        entry("ERRNO=%d", errno));
         elog<InternalFailure>();
     }
     smartSock.set(fd);