Increase timeout for storage engine tests

[davisp]

The compaction test takes quite a long time on purpose to show that we
can run a compaction that has many batches. On resource constrained
build machines like Jenkins and TravisCI this can end up taking longer
than the default 5s timeout.

Testing recommendations

Run the test suite on a resource constrained build machine (i.e., our Jenkins CI)

Checklist

• Code is written and works correctly;
• Changes are covered by tests;
• Documentation reflects the changes;