Clam 1106 clamdscan allmatch stickiness

[val-ms]

• Fix clamdscan --allmatch stickiness bug

  If you run clamdscan with the --allmatch option, it will cause all
  subsequent clamdscan scans to have all-match mode enabled.
  This bug is specific to clamd / clamdscan and does not affect clamscan.
  The problem was introduced when we converted the scan options from a
  single integer bitfield to a struct. The scan options set by the
  clamdscan parameters should be saved in a local copy of the scan
  options, but instead it is saving a copy of the pointer to the scan
  options struct, and so any changes to the scan options affect future
  scans.

• Test: Add clamdscan --allmatch stickiness regression test

  Test that clamdscan --allmatch does not cause future clamdscans to run
  in allmatch mode.

Fixes #276

[m-sola]

Comparison testing by running clamd, then clamdscan 3 times (no allmatch, allmatch, no allmatch):

In the previous version the last scan gave allmatch results.

Same test on this PR fixes that.

The code itself is straightforward. No issues there.