Clear all APF memory in testDropPingReply() in preparing stage

Modified testDropPingReply() to clear the entire APF memory instead of
only the first byte.  This addresses a known firmware issue with
handling programs smaller than 8 bytes.

Bug: 339147921
Test: TH
Change-Id: I651dae8c9daac24b195196c03b54e69a757de8a7
1 file changed