IPFSIntegrationTest may not stop camel contexts

IPFS integration tests do:

camelctx.start();
assumeIPFSAvailable(camelctx);

If a JUnit assumption fails (I.e when an IPFS connection is not available), then the test is immediately skipped before the Camel Context has been shut down.

This means there are unwanted CamelContext instances lingering in the CamelContextRegistry, which can make assertions in following integration tests fail.