kdbus: TEST_CREATE_CONN now does no depend on TEST_CREATE_BUS

kdbus: TEST_CREATE_CONN now does no depend on TEST_CREATE_BUS

Without this patch, it is impossible to specify test case able to
connect to a bus already created (e.g. by 'test-daemon' test case), you can
only specify:

1) TEST_CREATE_BUS which creates new bus, or
2) TEST_CREATE_CONN OR'ed with TEST_CREATE_BUS which creates new bus and
creates connection to it.

This patch adds the missing ability to specify TEST_CREATE_CONN alone.

It will be used by a new test case (will be added by separate commit) which
is supposed to connect to already started test-daemon case.

Change-Id: I10a4ccb76fa50a3b5f454f8e18031339f2f7d3d1
Signed-off-by: Paul Osmialowski <p.osmialowsk@samsung.com>