JCBC-426: Add support for manually disabling carrier or http bootstrap.

This changeset adds the possibility to manually disable both carrier and
http bootstrap through system properties.

Carrier: System.setProperty("cbclient.disableCarrierBootstrap", "true");
Http: System.setProperty("cbclient.disableHttpBootstrap", "true");

If such a setting is issued, a INFO level message is logged to make it easier
during debugging and failure analysis. Note that in general, tweaking such
params is not necessary, althogh it might help in certain debugging and
failure conditions.

Change-Id: I654bcecd0a1ffa576b7a5c146dc4580e37a7995e
Reviewed-on: http://review.couchbase.org/34380
Tested-by: Michael Nitschinger <michael.nitschinger@couchbase.com>
Reviewed-by: Matt Ingenthron <matt@couchbase.com>