fixes #5701 The assert half correct, half over-active. When the manager's mutex is held it is okay to transition an existing locktree's reference count from 0 to 1. If the lock isn't held, it's a race, since one thread could be destroying the zero-ref count locktree when you're incrementing the count. The failure occurred with the manager's mutx held (so the assert was overactive) and it's a layering-pain to assert that the manager's mutex is held otherwise, so just get rid of it.


git-svn-id: file:///svn/toku/tokudb@50297 c7de825b-a66e-492c-adef-691d508d4ae1