ubsan-test failed on Ubuntu 18.04

Host: ec2-100-24-72-44.compute-1.amazonaws.com
Project: WiredTiger (develop)
Commit: diff: WT-6177 direct I/O configurations fail with combined with mmap configurations (#5669)

• Remove trailing newlines from verbose message output.

• Don't allow mmap of any flavor to be configured with direct I/O.

• Don't configure direct I/O with any flavor of mmap.

• config.c:567:9: error: code will never be executed [-Werror,-Wunreachable-code]

• The "mmap" configuration defaults to on, and we have not historically had problems with combining
  it with direct I/O. Go back to allowing that combination. | 15 May 20 22:44 UTC
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