dreport: fix missing log messages related to skipping copy

Existing add_copy_file function not logging "skipping copy"
warning message incase dump size is reached to max size.

This message logging problem is fixed by call log function
prior to return call.

Tested: verified using dreport tool

Signed-off-by: Jayanth Othayoth <ojayanth@in.ibm.com>
Change-Id: I98ebe43e455e9b4cb93a102b7eb27e2a0f677309