system tests (logging): increase consistency delay

[stephenplusplus]

The recent push to master has introduced a new failed build (https://travis-ci.org/GoogleCloudPlatform/gcloud-node/jobs/145544257#L7638). We currently have two tests that will write log entries, then verify they were written properly by calling getEntries. We have a "write consistency delay" of 15 seconds that has worked in the past, but after testing with up to 2 minutes now, the call to getEntries still pulls old data.

This PR removes the delay, and simply checks that the "write entries" call doesn't fail.

@filipjs -- is there any reliable way to write a log entry, then pull it down from getEntries({ orderBy: 'timestamp desc', pageSize: 1 })?

[coveralls]

Coverage remained the same at 100.0% when pulling 5e80899 on stephenplusplus:spp--logging-test-rm-delay into 0c438e4 on GoogleCloudPlatform:master.

[filipjs]

We hit a small bump in our processing pipeline earlier today, probably that's why there were failures.
1 minute should be enough for that kind of test.

[stephenplusplus]

Ah, okay. Thanks for the info. I've updated the tests to allow 60 seconds before validating the entries.