Asks each content source associated with the given repo to synchronize the following information for the given repo:
- Package Metadata
- Package Bits
- Distribution Tree Metadata
- Distribution Tree Bits
@param repoId must indicate a valid repo in the database
@return
true
if the synchronize took place;
false
if it did not (for instance, if there is already a sync taking place for this repo)
@throws Exception if the data required to perform the sync is missing or invalid