Revert "Makefile: Add httpserver rule"

This reverts commit a39cde78. I applied
the broken version.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

modules/mgmt/Makefile

-module: httpserver
-
-httpserver:
-	cd ${OSV_BASE}/mgmt/httpserver && make -C
+module: