Merge branch 'be-wm-overrun-v2' * be-wm-overrun-v2: Fix hangs due to watermarks overruns in bufferevents implementations test: cover watermarks (with some corner cases) in ssl bufferevent Fixes: #690 (cherry picked from commit 878bb2d3b9484b27594308da1d0d6a7c9bdf6647)