Intermittently failing unit tests

[martinsumner]

Note these failure only appear to be an issue in CI.

module 'mochiweb_http'
  mochiweb_http: range_test...ok
  mochiweb_http: range_skip_length_test...ok
  module 'mochiweb_http_tests'
    mochiweb_http_tests:53: has_acceptor_bug_tests (1000 should be fine even with the bug)...[0.140 s] ok
    mochiweb_http_tests:55: has_acceptor_bug_tests (10000 should trigger the bug if present)...[0.002 s] ok
    undefined
    *** context setup failed ***
**in function mochiweb_http_tests:start_server/0 (test/mochiweb_http_tests.erl, line 36)
**error:{badmatch,{error,{already_started,<0.1278.0>}}}

leveled_cdb: get_keys_byposition_manykeys_test_...*failed*
in function leveled_cdb:'-get_keys_byposition_manykeys_test_to/0-fun-1-'/1 (src/leveled_cdb.erl, line 2364)
in call from leveled_cdb:get_keys_byposition_manykeys_test_to/0 (src/leveled_cdb.erl, line 2364)
**error:{assertMatch_failed,[{module,leveled_cdb},
                     {line,2364},
                     {expression,"cdb_getpositions ( P1 , 10 )"},
                     {pattern,"[ ]"},
                     {value,[69314,40802,53654,59486,65030,39110,55742,47174,
                             51386,70286]}]}

bitcask: fold_itercount_test_...*failed*
in function bitcask:'-fold_itercount_test2/0-fun-2-'/2 (src/bitcask.erl, line 3309)
in call from bitcask:fold_itercount_test2/0 (src/bitcask.erl, line 3309)
**error:{assertEqual_failed,[{module,bitcask},
                     {line,3309},
                     {expression,"Count2"},
                     {expected,0},
                     {value,1}]}

module 'prfDog'
  prfDog: t0_test...[1.807 s] ok
  prfDog: t1_test...
=INFO REPORT==== 22-Aug-2019::03:22:40 ===
    current_function: {prfHost,loop,1}
    line: 119
    lost_target: {killed,{gen_server,call,[prfDog,quit]}}

=INFO REPORT==== 22-Aug-2019::03:22:40 ===
    current_function: {prfTrc,idle,0}
    line: 65
    weird_in: {'EXIT',<0.392.0>,{killed,{gen_server,call,[prfDog,quit]}}}

=INFO REPORT==== 22-Aug-2019::03:22:40 ===
    current_function: {watchdog,mk_send_tcp,4}
    line: 541
    {didnt_make_subscriber,tcp,{badmatch,{error,econnrefused}}}
*timed out*
undefined

[martinsumner]

#1718

[martinsumner]

Since making the eper changes, overnight CI job has passed on develop-2.9 each night for a month.