Update drop count for HCP

[Sanjhana-Jayagopal]

What does this PR do?

Creates a flag to determine the drop count that will be added to the drop report.

• For HCP, the drop count will be the number of packets dropped since the last drop report that was sent to the AE.
• For simpleAE, the drop count will be the total number of packets dropped by the table entry match(direct_counter value). Existing tests will not break with this change.

  Do you have any concerns with this PR? No

  How can the reviewer verify this PR?

  Run the SDN controller with -drb argument as 'delta'. Execute the drop_rpt tests and validate drop_count using receive_packets.py on the AE.

  Any background context you want to provide? No

  Screenshots or logs (if appropriate)

  Questions:

• Have you connected this PR to the issue it resolves?
• Does the documentation need an update? No
• Does this add new dependencies? No
• Have you added unit or functional tests for this PR?

[spisarski]

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