Configure: fixed nobody/nogroup detection stderr redirection.

Previously, "grep: /etc/group: No such file or directory" errors were
printed on systems without the /etc/group file along with the configure
output.  Fix is to use correct stderr redirection.

Author: mdounin

auto/unix

@@ -7,13 +7,13 @@ NGX_USER=${NGX_USER:-nobody}
 
 if [ -z "$NGX_GROUP" ]; then
     if [ $NGX_USER = nobody ]; then
-        if grep nobody /etc/group 2>&1 >/dev/null; then
+        if grep nobody /etc/group >/dev/null 2>&1; then
             echo "checking for nobody group ... found"
             NGX_GROUP=nobody
         else
             echo "checking for nobody group ... not found"
 
-            if grep nogroup /etc/group 2>&1 >/dev/null; then
+            if grep nogroup /etc/group >/dev/null 2>&1; then
                 echo "checking for nogroup group ... found"
                 NGX_GROUP=nogroup
             else