Fix backward incompatibility in v1.2.1

[ackintosh]

related issue: #80

This fix is to ease the backward incompatibility in 1.2.1.

Unfortunately this does not completely fix the incompatibility. If you are using your custom adapter, please add setContext method like below in order to keep behaviors of your adapter.

If your custom adapter extends a built in adapter like below, it is recommended to use the parent implementation:

class CustomAdapter extends \Ackintosh\Ganesha\Storage\Adapter\Memcached
{
    // Comment out to use the parent implementation
    // public function setContext(Ganesha\Context $context): void
    // {
    // }
}

or if your custom adapter using no built in adapter, please add an empty setContext method to satisfy AdapterInterface requirement.

class CustomAdapter implements \Ackintosh\Ganesha\Storage\AdapterInterface
{
    public function setContext(Ganesha\Context $context): void
    {
         // nop
    }
}

[coveralls]

Coverage decreased (-0.3%) to 91.736% when pulling 7abb09a on fix-backward-incompatibility into a225863 on master.