Fix up DebugTest.

Fix ambiguous verify calls that somehow work on J7 but not J8.

Tidy imports, use Guava Sets instead of icky AICs.

Change-Id: I2638c0338a898454588ec435c83de849259f9133
Reviewed-on: http://gerrit.dmdirc.com/3564
Reviewed-by: Greg Holmes <greg@dmdirc.com>
Automatic-Compile: DMDirc Build Manager