relvalconsumer: sleep a bit before talking to PDC
per @threebean, PDC emits a fedmsg immediately the compose
importer runs, but database commit may not have run by then, so
the compose may not yet actually be queryable. I think we ran
into this race last night (the consumer reported that it could
not find all package versions), so let's sleep a bit before we
hit PDC for the package version check. According to Ralph, they
usually use 1 second sleeps for other similar cases, but PDC
import is a large operation so 10 seconds is probably safer.