worker/rsyslog: use namespace in the syslog tag

Without this, the syslog client may not be using the syslog tag
expected by rsyslogd on the state servers. This issue only affected
the local provider.

Fixes LP 1396796.
Merge pull request #1229 from mjs/syslog-client-tag-fix-1.21

worker/rsyslog: use namespace in the syslog tag

Without this, the syslog client may not be using the syslog tag expected by rsyslogd on the state servers. This issue only affected the local provider.

Fixes LP 1396796.

(Review request: http://reviews.vapour.ws/r/539/)