unit-test-long failed on ! Ubuntu 18.04

Host: ec2-107-23-243-58.compute-1.amazonaws.com
Project: WiredTiger (develop)
Commit: diff: WT-6556 Fix internal sessions to use internal session close function than public API to avoid memory leak (#5973)

Due to PANIC error set by the recovery failure stops processing
any session operations led to a memory leak. Using the internal
session close function Instead of public API by internal sessions
doesn't get stopped to close and it avoids the memory leak. | 31 Aug 20 00:10 UTC
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Task Logs

Signature:
[2020/08/31 01:14:58.401] ======================================================================
[2020/08/31 01:14:58.401] FAIL: test_prepare08.test_prepare08.test_prepare_delete_rollback (subunit.RemotedTestCase)
[2020/08/31 01:14:58.401] test_prepare08.test_prepare08.test_prepare_delete_rollback
[2020/08/31 01:14:58.401] ----------------------------------------------------------------------
[2020/08/31 01:14:58.401] _StringException: Traceback (most recent call last):
[2020/08/31 01:14:58.401] File "/data/mci/9c9a60042f7968434ca1f6366dfa21e5/wiredtiger/test/suite/test_prepare08.py", line 130, in test_prepare_delete_rollback
[2020/08/31 01:14:58.401] self.check(ds_1, uri_1, nrows, value_a, 20)
[2020/08/31 01:14:58.401] File "/data/mci/9c9a60042f7968434ca1f6366dfa21e5/wiredtiger/test/suite/test_prepare08.py", line 72, in check
[2020/08/31 01:14:58.401] self.assertEquals(cursor.get_value(),value)
[2020/08/31 01:14:58.401] File "/opt/mongodbtoolchain/revisions/6856ed66de820bd93fda1c07004fff10e7d48b2f/stow/python2-v3.yy3/lib/python2.7/unittest/case.py", line 513, in assertEqual
[2020/08/31 01:14:58.401] assertion_func(first, second, msg=msg)
[2020/08/31 01:14:58.401] File "/opt/mongodbtoolchain/revisions/6856ed66de820bd93fda1c07004fff10e7d48b2f/stow/python2-v3.yy3/lib/python2.7/unittest/case.py", line 506, in _baseAssertEqual
[2020/08/31 01:14:58.401] raise self.failureException(msg)
[2020/08/31 01:14:58.401] AssertionError: 'bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb' != 'aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa'
[2020/08/31 01:14:58.401] ----------------------------------------------------------------------