pkd: a few improvements and fixups

Summary:
Hello, resending this patch series for the `pkd` tests, originally
sent to the mailing list here:

 *  https://www.libssh.org/archive/libssh/2017-07/0000011.html

Here are a few improvements and fixups for the `pkd` tests, including
a new flag `-m` that can be used to run only certain subsets of the
test passes.

Jon Simons (5):
  pkd: rename AES192 cipher suite -> OPENSSHONLY
  pkd_daemon.c: mark `pkd_ready` field as volatile
  pkd: fixups for updated CMocka CMUnitTest struct
  pkd: refactor -t testname lookup-by-name
  pkd: support -m to match multiple tests

 tests/pkd/pkd_daemon.c |  2 +-
 tests/pkd/pkd_daemon.h |  1 +
 tests/pkd/pkd_hello.c  | 84 +++++++++++++++++++++++++++++++++-----------------
 3 files changed, 58 insertions(+), 29 deletions(-)

--

Test Plan:
 * I've been using the new `-m` mode locally for a long time to run
   only certain groups of tests.

 * The CMocka struct fixes can be seen in the pkd output before and
   after: after, there are no more extraneous test output strings.

 * The fix for the `pkd_ready` field can be observed when building
   the libssh tests with `-Os` on a Debian system (before the fix,
   pkd would hang, after the fix, it runs as intended).

Reviewers: asn

Reviewed By: asn

Tags: #libssh

Differential Revision: https://bugs.libssh.org/D2

tests/pkd/pkd_daemon.c

@@ -58,7 +58,7 @@ static struct {
     int rc;
     pthread_t tid;
     int keep_going;
-    int pkd_ready;
+    volatile int pkd_ready;
 } ctx;
 
 static struct {