poldek --up should not cancel other actions

[Elan Ruusamäe]

i'm using mixed repos (type dir and type pndir), and would like to run --update and --upgrade commands in same commandline.
it works fine if all repos are pndir, but it says WARNING, but really aborts actual upgrade command, and exit code is set to error too, so it's not WARNING as it displays it:

# poldek --sn th --st=dir -s /var/lib/jenkins/jobs/job/workspace/build/rpm/ --up -u package ; echo RC=$?
warn: /var/lib/jenkins/jobs/job/workspace/build/rpm/: this type (dir) of source is not updateable

Retrieving th::packages.ndir.md...
th is up to date

Retrieving th::packages.ndir.md...
th is up to date

RC=1