bpo-37558: Shared memory tests are failing due to double slashes (GH-14703)

With the addition of shared memory into Python 3.8, we now have three tests failing on Solaris, namely `test_multiprocessing_fork`, `test_multiprocessing_forkserver` and `test_multiprocessing_spawn`. The reason seems to be incorrect name handling which results in two slashes being prepended.

https://bugs.python.org/issue37558
(cherry picked from commit 4737265)

Co-authored-by: Jakub Kulík <[email protected]>

Author: miss-islington

Lib/test/_test_multiprocessing.py

@@ -3990,7 +3990,7 @@ def test_shared_memory_cleaned_after_process_termination(self):
 
             # Create a shared_memory segment, and send the segment name
             sm = shared_memory.SharedMemory(create=True, size=10)
-            sys.stdout.write(sm._name + '\\n')
+            sys.stdout.write(sm.name + '\\n')
             sys.stdout.flush()
             time.sleep(100)
         '''

Misc/NEWS.d/next/Tests/2019-07-11-10-33-56.bpo-37558.SKHRsL.rst

@@ -0,0 +1 @@
+Fix test_shared_memory_cleaned_after_process_termination name handling