some of our tests are flaky (was: FAIL: sampling_test src/tests/sampling_test.cc:122 Check failed: 50 <= percent)

[00:00:38] + make -j32 check VERBOSE=1
...
[00:00:39] ./test-driver: line 112: 450805 Aborted                 "$@" >> "$log_file" 2>&1
[00:00:39] FAIL: sampling_test
...
[00:01:02] ==========================================
[00:01:02]    gperftools 2.15.90: ./test-suite.log
[00:01:02] ==========================================
[00:01:02] 
[00:01:02] # TOTAL: 55
[00:01:02] # PASS:  54
[00:01:02] # SKIP:  0
[00:01:02] # XFAIL: 0
[00:01:02] # FAIL:  1
[00:01:02] # XPASS: 0
[00:01:02] # ERROR: 0
[00:01:02] 
[00:01:02] .. contents:: :depth: 2
[00:01:02] 
[00:01:02] FAIL: sampling_test
[00:01:02] ===================
[00:01:02] 
[00:01:02] Using local file /usr/src/RPM/BUILD/gperftools-2.15.90/.libs/lt-sampling_test.
[00:01:02] Using local file /usr/src/tmp/sampling_test.heap.fdsBLs.
[00:01:02] Adjusting heap profiles for 1-in-524288 sampling rate
[00:01:02] Heap version 2
[00:01:02] src/tests/sampling_test.cc:122 Check failed: 50 <= percent
[00:01:02] FAIL sampling_test (exit status: 134)
[00:01:02] 
[00:01:02] ============================================================================
[00:01:02] Testsuite summary for gperftools 2.15.90
[00:01:02] ============================================================================
[00:01:02] # TOTAL: 55
[00:01:02] # PASS:  54
[00:01:02] # SKIP:  0
[00:01:02] # XFAIL: 0
[00:01:02] # FAIL:  1
[00:01:02] # XPASS: 0
[00:01:02] # ERROR: 0
[00:01:02] ============================================================================
[00:01:02] See ./test-suite.log
[00:01:02] Please report to [email protected]
[00:01:02] ============================================================================