Sample 'api' debug log group at 1:1000

api.log on fluorine now routinely exceeds 100GB, which fills up the disk on
that host, and which is too large to be analyzed quickly in the shell. So
sample the api log at 1:1000, using the configuration option introduced in
2c25e14642b8.

Change-Id: Id9023e66c94b43899ad69dd82f4556b6308739f3
Merge "Sample 'api' debug log group at 1:1000"