493037: Check if a task is in unmatched before removing from unmatched

This gives a considerable performance increase when loading large task
lists where there are more tasks than any one task has parents.

Change-Id: I18ccd3ba7387d937b78fb21e766d299f2a88491b
Task-Url: https://bugs.eclipse.org/bugs/show_bug.cgi?id=493037
Signed-off-by: Jaxsun McCarthy Huggan <jaxsun.mccarthy@tasktop.com>
2 files changed