dreport: Added error handling support in badvpd

This is to fix below error message in the journal logs.
cp: can't stat '/tmp/bad-vpd': No such file or directory

"bad-vpd" is an optional file created vpd, to store the
failing data.

Tested:  verified using dreport command line tool
    "INFO: No Bad VPD data"

Signed-off-by: Jayanth Othayoth <ojayanth@in.ibm.com>
Change-Id: I56854c044d5479f48669736204d9b929fc5d8db5