Chnage to use static event type name

	modified:   trace/net.sf.milkfish.systrace.core/src/net/sf/milkfish/systrace/core/cache/TraceLoader.java
Change to guava list cache load

	modified:   trace/net.sf.milkfish.systrace.core/src/net/sf/milkfish/systrace/core/cache/TraceLoader.java