unmakeVarBinds shouldn't not ignore errors

[therve]

In that commit: https://github.com/etingof/pysnmp/commit/e8fa401677432e4e48d1a9c36b996ef94b043d90#diff-dfd8cef40427a8ae7a84575d7e419aa7R74 unmakeVarBinds was not change to pass ignoreErrors=False.

It seems like a backward incompatible change. Overall, I feel that resolveWithMib should have had False as a default from the beginning, but maybe it's too late.

[lextm]

This was an intentional change made by Ilya, if you read the comments of that commit,

This change tightens outgoing objects MIB compliance (send will fail), but tolerate non quite compliant objects we receive.

Since unmakeVarBinds are only used on received messages, it makes sense to use ignoreErrors=True.

Anyway this flag isn't very useful based on my observations.