server: mock ExecResponse
server: mock ExecResponse

This patch prevents k8s's e2e_node tests from killing CRI-O (because of
a panic in marshaling nil responses). This will ensure tests keep
running and just logging the failure.

Signed-off-by: Antonio Murdaca <f9809039ea4850e75dcb8d80b778844aa463358f@redhat.com>

vbatts/cri-o,kubernetes-incubator/ocid,mheon/cri-o,umohnani8/cri-o,aweiteka/cri-o,umohnani8/cri-o,kubernetes-incubator/cri-o,rhatdan/cri-o,apilloud/cri-o,jwhonce/ocid,kubernetes-incubator/cri-o,jwhonce/ocid,aweiteka/cri-o,kubernetes-incubator/ocid,apilloud/cri-o,rhatdan/cri-o,mikebrow/cri-o,14rcole/cri-o,14rcole/cri-o,mheon/cri-o,umohnani8/cri-o,vbatts/cri-o,kubernetes-incubator/cri-o,kubernetes-incubator/cri-o,14rcole/cri-o,nalind/cri-o,apilloud/cri-o,nalind/cri-o,aweiteka/cri-o,14rcole/cri-o,mheon/cri-o,rhatdan/cri-o,mheon/cri-o,kubernetes-incubator/ocid,mikebrow/cri-o,rhatdan/cri-o,nalind/cri-o,jwhonce/ocid,vbatts/cri-o,mikebrow/cri-o,umohnani8/cri-o,vbatts/cri-o,mikebrow/cri-o