socket/glusterd/client: enable SSL for management

The feature is controlled by presence of the following file:

	/var/lib/glusterd/secure-access

See the comment near the definition of SECURE_ACCESS_FILE in glusterfs.h
for the rationale.  With this enabled, the following rules apply to
connections:

	UNIX-domain sockets never have SSL.

	Management-port sockets (both connecting and accepting, in
	daemons and CLI) have SSL based on presence of the file.

	Other IP sockets have SSL based on the existing client.ssl and
	server.ssl volume options.

Transport multi-threading is explicitly turned off in glusterd (it would
otherwise be turned on when SSL is) due to multi-threading issues.
Tests have been elided to avoid risk of leaving a file which will cause
all subsequent tests to run with management SSL still enabled.

IMPLEMENTATION NOTE
The implementation is a bit messy, and consists of two stages.  First we
decide whether to set the relevant fields in our context structure, based
on presence of the sentinel file OR a command-line override.  Later we
decide whether a particular connection should actually use SSL, based on the
context flags plus what kind of connection we're making[1] and what kind of
daemon we're in[2].

[1] inbound, outbound to glusterd port, other outbound
[2] glusterd, glusterfsd, other

TESTING NOTE
Instead of just running one special test for this feature, the ideal
would be to run all tests with management SSL enabled.  However, it
would be inappropriate or premature to set up an optional feature in the
patch itself.  Therefore, the method of choice is to submit a separate
patch on top, which modifies "cleanup" in include.rc to recreate the
secure-access file and associated SSL certificate/key files before each
test.

Change-Id: I0e04d6d08163893e24ec8c031748c5c447d7f780
BUG: 1114604
Signed-off-by: Jeff Darcy <jdarcy@redhat.com>
Reviewed-on: http://review.gluster.org/8094
Tested-by: Gluster Build System <jenkins@build.gluster.com>
Reviewed-by: Vijay Bellur <vbellur@redhat.com>