Add sleep before fetching reports

Attempt to fix MetricActivationTests#testMultipleActivations.

Bug: 273653654
Test: atest --no-bazel-mode --retry-any-failure 5
CtsStatsdHostTestCases: android.cts.statsd.metric.MetricActivationTests\#testMultipleActivations
Change-Id: Id0627ad63966fefa9790951265d4f6b6647ec851
1 file changed