reset cluster context errors in redisClusterAsyncFormattedCommandToNode

[andreasgerstmayr]

Analogue to redisClusterAsyncFormattedCommand, where the acc and acc->cc
errors are reset before sending the request.

Reason: The redisClusterAsyncCallback callback checks acc->err and omits the
reply if it is set.

[zuiderkwast]

Good, I guess. Is a test case too much to ask? ;-)

[andreasgerstmayr]

@zuiderkwast that's actually not as easy as it sounds ;) - afaics I'll need to create a new test script in tests/scripts/ which uses simulated-redis.pl in order to simulate an intermediate Redis disconnect (I need to get a NULL reply from hiredis to make redisClusterAsyncCallback set the acc->err flag)?

I'll look into that next week.

[zuiderkwast]

that's actually not as easy as it sounds ;)

Oh, well, maybe we can accept this PR without a test then. @bjosv WDYT?

A test is of course very welcome, but perhaps not blocking. (I spent some time with these Perl scripts for testing ASK redirects. I hope you like the way these scripts work, and Perl. :-D)

[bjosv]

I think its ok without a test for now, we don't have any for the similar case of redisClusterAsyncFormattedCommand() ..but a test would sure be great.

[zuiderkwast]

OK, fine with me then. I haven't followed the code around enough to see if this is right, but if you're confident @bjosv, feel free to merge!

[andreasgerstmayr]

Thanks for merging! Test is in #68.