mod_netconf: fixed problem with RPM generation

configure script initializes CFLAGS variable with '-O2' flag that is
unknown to apxs -> rewrite with new value

- refs #643
diff --git a/src/configure b/src/configure
index ff8497e..65e6dd7 100755
--- a/src/configure
+++ b/src/configure
@@ -2226,7 +2226,7 @@
 
 fi
 
-CFLAGS="$CFLAGS $LIBNETCONF_CFLAGS"
+CFLAGS="$LIBNETCONF_CFLAGS"
 LIBS="$LIBS $LIBNETCONF_LIBS"