8. uninit_use: Using uninitialized value "value".
Restructure so we drop core if there's a problem (initialize
key & value to NULL), and we don't read "value" unless it's
been initialized.
success.
Add additional wording that WT_CURSOR::reset should be called after any
of the WT_CURSOR search, search-near, update or remove methods, once
the cursor is no longer being used to iterate or retrieve values.
Closes#587.
