Tests: relax the assertion on circuit breakers jmx output (especially the limit)
Tests: relax the assertion on circuit breakers jmx output (especially the limit)

We encountered some flakyness on asserting the exact value of the CB limit
in jenkins so this commit changes the assertion on the exact value to
verify that the value is positive.

crate/crate,EvilMcJerkface/crate,crate/crate,EvilMcJerkface/crate,EvilMcJerkface/crate,crate/crate