runtime/v2/shim: return if error in load plugin
runtime/v2/shim: return if error in load plugin

If there is any unskipable error during setuping shim plugins, we should
fail return error to prevent from leaky shim instance. For example,
there is error during init task plugin, the shim ttrpc server will not
contain any shim API method. The any call to the shim will receive that

  failed to create shim task: service containerd.task.v2.Task: not implemented

Then containerd can't use `Shutdown` to let the shim close. The shim
will be leaky. And also fail return if there is no ttrpc service.

Signed-off-by: Wei Fu <df4176d36abdc6fd0d966de5d5471522668de494@gmail.com>

thaJeztah/containerd,mikebrow/containerd,containerd/containerd,mikebrow/containerd,containerd/containerd,estesp/containerd,estesp/containerd,thaJeztah/containerd