Do not populate StoreEntry basics from Transients (#1343)

Do not populate StoreEntry basics from Transients (#1343)

    client_side_reply.cc:1078: "http->storeEntry()->objectLen() >= 0"
    inside clientReplyContext::storeOKTransferDone()

Since commit 24c9378, Transients are not supposed to maintain "basic"
cache entry information (i.e. StoreMapAnchor::Basics a.k.a. StoreEntry
STORE_META_STD fields). Using often-at-their-defaults Transient basics
may unexpectedly erase valuable StoreEntry information obtained from one
of the caches (e.g., swap_file_sz) and lead to assertions.

Consequently, do not populate unused Transients entry basics either.

Eventually, we may find a good way to parameterize StoreMapAnchor to
avoid keeping those unused fields in Transients StoreMap.