Add cache clear on error for inc, touch, delete_many, add

[nessex]

This adds django-elasticache's exception handling to additional cache commands.
We were seeing some commands executed in a recent incident with logs suggesting the response was for a different type of command entirely. This could have been caused by any of these commands hitting exception cases like timeouts, then the response buffer being reused despite being half-full of data from the failed request.

I'm speculating a little, and we won't necessarily be able to see the issue without the accompanying timeouts / exceptions to verify, but it seems like a safe change to make. This certainly isn't the only thread safety issue in our cache library stack though.

Note: The original author even acknowledged the problem here, but the PR stalled due to unrelated changes
gusdan#27 (comment)