RFR: 256: Multiple [Integrated] messages can still be sent

[Robin Westberg]

Hi all,

Please review this follow-up fix for SKARA-248.

Best regards,
Robin

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Commits:
 - c4c2509e: Make TestMailmanServer behave more like pipermail

Changes: https://git.openjdk.java.net/skara/pull/391/files
 Webrev: https://webrevs.openjdk.java.net/skara/391/webrev.00
  Issue: https://bugs.openjdk.java.net/browse/SKARA-256
  Stats: 31 lines in 4 files changed: 8 ins; 8 del; 15 mod
  Patch: https://git.openjdk.java.net/skara/pull/391.diff
  Fetch: git fetch https://git.openjdk.java.net/skara pull/391/head:pull/391

PR: https://git.openjdk.java.net/skara/pull/391