Make syslog-ng basepath a parameter

For beta we will have to write syslog on a different path than
/home/wikipedia/syslog.  This patch removes the hardcoded value from the
syslog-ng configuration and explicitly pass the class parameter on the
nfs1 and nfs2 production hosts.

Bug: 62757
Change-Id: I4ec49ba38634adbe9156dcdd82c73a91987fd607