[findbugs] Do not ignore exceptional return value of mkdir

java.io.File.mkdir() and mkdirs() report failure as an exceptional
return value false. Fix the code which silently ignored this
exceptional return value.

Change-Id: I41244f4b9d66176e68e2c07e2329cf08492f8619
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>
23 files changed