The LRU chain management code was broken leading to situations where
the chain was incomplete. This prevented the cache from removing
items when it exceeded its memory target, causing a leak.
One case was repeated hit on the head of the chain. moveToHead(e)
was invoked linking the head back to itself in a cycle orphaning
the rest of the table.
Add some unit tests to cover this and a few other paths.
Change-Id: Ib27486eaa1b1d2bf1c745a56d0a5832bfb029322
8ff08455f6