Currently, if the test fail, pytest will output only some basic information about the fail. With this change, it will output the last 300 lines of the boost/seastar test output. Also add capturing the output of the failed tests to JUnit report, so it will be present in the report on Jenkins. Fixes: https://scylladb.atlassian.net/browse/SCYLLADB-449 Closes scylladb/scylladb#28535