Avoid long running transaction in test_truncate15

test_commands

WT_BUILDDIR=$(git rev-parse --show-toplevel)/cmake_build DYLD_LIBRARY_PATH=$WT_BUILDDIR python3 ../test/suite/run.py -v 2 -j $(sysctl -n hw.logicalcpu) 2>&1

Link: https://evergreen.mongodb.com/task_log_raw/wiredtiger_macos_1014_unit_test_929c31276ce6d64095eca4d00fe82c703618a336_22_07_29_03_16_17/0?type=T#L13

Test failure

ERROR: test_truncate15.test_truncate15.test_truncate15(truncate.integer_row) (subunit.RemotedTestCase)

test_truncate15.test_truncate15.test_truncate15(truncate.integer_row)

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testtools.testresult.real._StringException: Traceback (most recent call last):

  File "/data/mci/585a746d1a89f17e9b5be2bce8e60131/wiredtiger/test/suite/wttest.py", line 328, in _callTestMethod

    method()

  File "/data/mci/585a746d1a89f17e9b5be2bce8e60131/wiredtiger/test/suite/test_truncate15.py", line 147, in test_truncate15

    cursor[ds.key(i)] = value_a

  File "/data/mci/585a746d1a89f17e9b5be2bce8e60131/wiredtiger/cmake_build/lang/python/wiredtiger/swig_wiredtiger.py", line 323, in __setitem__

    if self.insert() != 0:

_wiredtiger.WiredTigerRollbackError: WT_ROLLBACK: conflict between concurrent operations

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Ran 9860 tests in 8326.591s

Link: https://evergreen.mongodb.com/task_log_raw/wiredtiger_macos_1014_unit_test_929c31276ce6d64095eca4d00fe82c703618a336_22_07_29_03_16_17/0?type=T#L36239

Evergreen YAML Script Failure

Command failed: shell script encountered problem: exit code 1

Link: https://evergreen.mongodb.com/task_log_raw/wiredtiger_macos_1014_unit_test_929c31276ce6d64095eca4d00fe82c703618a336_22_07_29_03_16_17/0?type=T#L36255