Fix wrong Guice wiring

BanCommit and SuggestParentCandidates Guice beans were using assisted
inject pattern.  The factories were bound in request scope module even
though both beans have nothing to do with request scope.

Fix it by dropping unnecessary assisted inject bindings and move the
beans into singleton scope.

Change-Id: Ia792fb0db60e594456034c1517468a309393f5b5
5 files changed