CacheInterface.h: make CkCache.h an angled #include

Needed for similar reason as described in commit @c9a512e: ChaNGa's
dependency generation assumes that CkCache.h is a local include, and here
the files _it_ includes (using quoted-style inclusion) were being listed without 
path in Makefile.dep.

Ran into an issue with this on Lonestar, when compiling with GCC 4.4.5.