"Find pattern in MSA" task changes selection even if a user does a drag and drop action right in this moment

Scenario:

1. Open "data/samples/CLUSTALW/COI.aln".
2. Open "Search in Alignment" options panel tab.
3. Enter pattern "ACGT".
4. Wait until the search task is finished.
   Expected result: there are several results, the first one is somewhere in the third sequence ("Bicolorana_bicolor_EF540830").
5. Click on the "Bicolorana_bicolor_EF540830" sequence name. Do not release the mouse button.
6. Drag the sequence name to the next position (to the forth position). Do not release the mouse button.
   Expected result: the search task in NOT relaunched (see UGENE-6689).
   Actual result: the search task is relaunched.
7. Wait for the search task to complete.
   Actual result: the search task sets the selection to the first found subsequence. The result is in the "Roeseliana_roeseli" sequence. The "Roeseliana_roeseli" sequence name becomes selected.
8. Move the mouse cursor to the next position in the name list (to the fifth position).
   Expected result: "Bicolorana_bicolor_EF540830" is moved to the fifth position.
   Actual result: "Bicolorana_bicolor_EF540830" is moved to the third position, "Roeseliana_roeseli" is moved to the forth position.

The search task shouldn't interrupt the user's action.