Fix missing errno.h includes after libc cleanup.

These issues hadn't been found yet because a libc++ header was
unconditionally pulling in errno.h. I've fixed the libc++ header now.

Change-Id: Ib096634cdd231fc75bf7548e4b99babc7442dc53
diff --git a/server/NetdConstants.cpp b/server/NetdConstants.cpp
index 4823c91..8423fd6 100644
--- a/server/NetdConstants.cpp
+++ b/server/NetdConstants.cpp
@@ -14,14 +14,15 @@
  * limitations under the License.
  */
 
+#include <ctype.h>
+#include <errno.h>
 #include <fcntl.h>
 #include <netdb.h>
+#include <net/if.h>
 #include <netinet/in.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/wait.h>
-#include <ctype.h>
-#include <net/if.h>
 
 #define LOG_TAG "Netd"