c878226a2b
Aligns the signatures of client initialization methods with those used for origin initialization, primarily by adding the aCreateIfNonExistent parameter. This change prepares the way for supporting delayed creation of client directories in QuotaManager::OpenClientDirectory, as required by the LSNG quota client. LSNG delays creation of origin and client directories for performance reasons, and this refactoring ensures that behavior can be preserved when client initialization is added to OpenClientDirectory. Differential Revision: https://phabricator.services.mozilla.com/D246563