Adjust our tests for upcoming migration of the default value for the
"push.default" configuration variable to "simple" from "mixed".
* 'jc/push-2.0-default-to-simple' (early part):
t5570: do not assume the "matching" push is the default
t5551: do not assume the "matching" push is the default
t5550: do not assume the "matching" push is the default
t9401: do not assume the "matching" push is the default
t9400: do not assume the "matching" push is the default
t7406: do not assume the "matching" push is the default
t5531: do not assume the "matching" push is the default
t5519: do not assume the "matching" push is the default
t5517: do not assume the "matching" push is the default
t5516: do not assume the "matching" push is the default
t5505: do not assume the "matching" push is the default
t5404: do not assume the "matching" push is the default