dirmngr: Only use SKS pool CA for SKS pool

dirmngr: Only use SKS pool CA for SKS pool

* dirmngr/http.c (http_session_new): when checking whether the
keyserver is the HKPS pool, check specifically against the pool name,
as ./configure might have been used to select a different default
keyserver.  It makes no sense to apply Kristian's certificate
authority to anything other than the literal host
hkps.pool.sks-keyservers.net.

Signed-off-by: Daniel Kahn Gillmor <dkg@fifthhorseman.net>
(cherry picked from commit 3233382068b7c477907daac697164b81ae45a7f4)

Gbp-Pq: Topic keyserver-cleanup
Gbp-Pq: Name dirmngr-Only-use-SKS-pool-CA-for-SKS-pool.patch