Omit debug output in case there is no value given.

Change-Id: Icad15ff57876947f6c07ce940f2395bfdb547a37
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
add resetCheckSumData

 - Getting the redirect information was handled as general data.
   This resulted in a wrong sha1sum. Now the calculated sha1sum is
   reseted after getting a HTTP redirect.

Change-Id: I3aebe33fea7091e8dc3cfeddc1feee4a50e2a748
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>