Allow to run tests without CouchbaseMock.jar

Fixes binary package builders (DEB/RPM)

Change-Id: I780b01ddd2b2c185136258de7e65798467766a49
Reviewed-on: http://review.couchbase.org/28224
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Reviewed-by: Trond Norbye <trond.norbye@gmail.com>
Add example for a multicluster client

Change-Id: Ie3924550c07ed92096c5a90b7aa0a595daa6cd65
Reviewed-on: http://review.couchbase.org/28221
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Use TESTS_ENVIRONMENT rather than AM_TESTS_ENVIRONMENT

Change-Id: I7f0f5e7b76d6a508227f5d3afd9ce5c570871dc0
Reviewed-on: http://review.couchbase.org/28225
Reviewed-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Tested-by: Sergey Avseyev <sergey.avseyev@gmail.com>
Allow to run 'make check' without plugins

Because of built-in 'select' plugin, most of examples and cbc can be
built without dynamic plugins

Change-Id: Ie76692d1740228c17edd75763e531fb3c429780c