Go easier on OSS Sonatype when deploying

It seems that as of May 20th, 2014, deploying to OSS Sonatype became
substantially slower. Even if the load on Sonatype should lighten,
we should be more lenient than giving it only five minutes to perform
all the checks before closing the staging repository.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>