Because no localdisk means either s3 or google is the primary,
and none of them support efficient replication.
1) Added a dummy synchandler constructor for when config has "idle"
2) Set "idle" for synchandler config when no localdisk
3) fixed corresponding tests
Also:
- added error (and test) when no localdisk and both s3 and google
in config
- added s3 + mysql test
http://camlistore.org/issue/201
Change-Id: I861fdca0c203bc0181ab6d548adab501ed98d2f0
mpl