See also https://github.com/zopefoundation/ZEO/pull/63
     and !1095

No error in testCMFActivity and testConflictResolution.
For the only error in testInvalidationBug, see comment.

But this commit is not enough for ZODB5. The only known issue so far
is the use of newer pickle protocol, which breaks export of ZODB data
and requires non-trivial changes in our XMLExportImport/ppml code.
So for the moment, many failures in testBusinessTempate.