macOS installer build: mitigate hdiutil resource busy bug

[ned-deily]

No description provided.

[miss-islington]

@ned-deily: Status check is done, and it's a success ✅ .

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 FreeBSD 10-STABLE Non-Debug 3.x has failed when building commit 0133f9f.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/167/builds/425) and take a look at the build logs.
4. Check if the failure is related to this commit (0133f9f) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/167/builds/425

Click to see traceback logs

Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/test/test_socket.py", line 5797, in testWithTimeoutTriggeredSend
    conn = self.accept_conn()
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/test/test_socket.py", line 5607, in accept_conn
    conn, addr = self.serv.accept()
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/socket.py", line 212, in accept
    fd, addr = self._accept()
socket.timeout: timed out

======================================================================
ERROR: testWithTimeoutTriggeredSend (test.test_socket.SendfileUsingSendTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/test/test_socket.py", line 335, in _tearDown
    raise exc
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/test/test_socket.py", line 353, in clientRun
    test_func()
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/test/test_socket.py", line 5791, in _testWithTimeoutTriggeredSend
    with socket.create_connection(address, timeout=0.01) as sock, \
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/socket.py", line 727, in create_connection
    raise err
  File "/usr/home/buildbot/python/3.x.koobs-freebsd10.nondebug/build/Lib/socket.py", line 716, in create_connection
    sock.connect(sa)
socket.timeout: timed out

----------------------------------------------------------------------

Ran 567 tests in 35.477s

FAILED (errors=2, skipped=61)