jqueue: make replication on job update optional
jqueue: make replication on job update optional

Sometimes it's useful to write to the local filesystem, but immediate
replication to all master candidates is not needed.

The _WriteAndReplicateFileUnlocked function gets renamed to
_UpdateJobQueueFile, as calling "write and replicate, but don't
replicate" seemed a bit strange.

Signed-off-by: Guido Trotter <f62ca4d5358bdaeef0e50e57f9f7e231de63727e@google.com>
Reviewed-by: Michael Hanselmann <68b67885ff74281219b4a4be33cc20fd45078d7c@google.com>

ganeti-github-testing/ganeti-test-1,ganeti/ganeti,apyrgio/snf-ganeti,grnet/snf-ganeti,yiannist/ganeti,mbakke/ganeti,ganeti-github-testing/ganeti-test-1,andir/ganeti,bitemyapp/ganeti,leshchevds/ganeti,leshchevds/ganeti,ganeti/ganeti,onponomarev/ganeti,yiannist/ganeti,dimara/ganeti,yiannist/ganeti,apyrgio/ganeti,mbakke/ganeti,onponomarev/ganeti,dimara/ganeti,grnet/snf-ganeti,andir/ganeti,leshchevds/ganeti,bitemyapp/ganeti,mbakke/ganeti,apyrgio/snf-ganeti,apyrgio/ganeti,andir/ganeti,ganeti/ganeti