os/FileStore: kludge sloppy hammer temp objects into temp collection

os/FileStore: kludge sloppy hammer temp objects into temp collection

When we are running with a mixed hammer cluster, hammer primaries
will generate temp object names that are sloppy.  Make sure we still
put them into the temp collection.

Note that this isn't a problem on write because the primary (hammer)
OSD generated the transaction and explicitly specified a temp
collection; it's only transactions we do on our own with the sloppy
temp ghobject_t that trip over this.

Fixes: #13395
Signed-off-by: Sage Weil <sage@redhat.com>