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.in b/src/configure.in
index 4e56d69..191a51a 100644
--- a/src/configure.in
+++ b/src/configure.in
@@ -39,7 +39,7 @@
 	PKG_CHECK_MODULES(LIBNETCONF, libnetconf)
     BUILDREQS="$BUILDREQS ,libnetconf-devel"]
 )
-CFLAGS="$CFLAGS $LIBNETCONF_CFLAGS"
+CFLAGS="$LIBNETCONF_CFLAGS"
 LIBS="$LIBS $LIBNETCONF_LIBS"
 AC_SUBST([LIBNETCONF_LIBS])
 AC_SUBST([LIBNETCONF_CFLAGS])