e - ibar - fix clash when 2 icons of the same path get added somehow
i encontered a situation where the icon_hash contained a garbage entry
- had been freed already. the only way i can see this happening is if
the desktop file changed path during runtime thus the icon was never
removed from hash on free as string didnt match. store string used
when adding to hash so removal is guarannteed to work and also for
good measure protect against double-adding (and generate a new string
for storage using timestamp which should be unique).
so this fixes a crash i was just looping on.