Remove libcurl support from update_engine_sideload.

While sideloading an update from recovery we don't need nor want to
download payload from HTTP(S) URLs, only local file:// are supported.
This patch moves libcurl_http_fetcher and certificate_checker files out
of libpayload_consumer dropping the libcurl and libssl dependencies from
it and the update_engine_sideload.

Bug: 27178350
TEST=build UE for Brillo and Android. Unittests still pass and
update_engine_sideload doesn't link to libcurl.

Change-Id: Iffefdb094654f7277dc825c041fe55aac9ee8756
diff --git a/real_system_state.h b/real_system_state.h
index ec17117..0964f10 100644
--- a/real_system_state.h
+++ b/real_system_state.h
@@ -25,8 +25,8 @@
 #include <metrics/metrics_library.h>
 #include <policy/device_policy.h>
 
+#include "update_engine/certificate_checker.h"
 #include "update_engine/common/boot_control_interface.h"
-#include "update_engine/common/certificate_checker.h"
 #include "update_engine/common/clock.h"
 #include "update_engine/common/hardware_interface.h"
 #include "update_engine/common/prefs.h"