Flush ContributionRecur static cache when flushing processors

[eileenmcnaughton]

Overview

Ensures a (new) static cache is flushed when creating a processor, mostly useful for unit testing

Before

Cache not flushed

After

Cache flushed

Technical Details

When creating a processor in a unit test it may not be available to use when creating
a recurring in the same test without flushing the static cache here

Comments

This hit our WMF unit tests

[civibot]

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[eileenmcnaughton]

unrelated fail