Add Container object to environment build and runtime specs (#413)

Environment Specs so far had only an image URL to specify a container image.

This was fine for public images but fell short in a few of cases:
(a) Using private image registries
(b) Specifying environment variables (this is needed for workflows helm install)
(c) Setting a SecurityContext for the container

This change adds the Container object to both build and runtime Environments. 

Compatibility is preserved -- the existing ImageURL field is still used.  See the comments in types.go for the overriding rules in the case that both Container and ImageURL are specified.

executor/newdeploy/newdeploy.go

@@ -193,7 +193,7 @@ func (deploy *NewDeploy) getDeploymentSpec(fn *crd.Function, env *crd.Environmen
 						},
 					},
 					Containers: []apiv1.Container{
-						{
+						fission.MergeContainerSpecs(&apiv1.Container{
 							Name:                   fn.Metadata.Name,
 							Image:                  env.Spec.Runtime.Image,
 							ImagePullPolicy:        apiv1.PullIfNotPresent,
@@ -223,7 +223,7 @@ func (deploy *NewDeploy) getDeploymentSpec(fn *crd.Function, env *crd.Environmen
 								},
 							},
 							Resources: resources,
-						},
+						}, env.Spec.Runtime.Container),
 						{
 							Name:                   "fetcher",
 							Image:                  deploy.fetcherImg,

executor/poolmgr/gp.go

@@ -524,7 +524,7 @@ func (gp *GenericPool) createPool() error {
 						},
 					},
 					Containers: []apiv1.Container{
-						{
+						fission.MergeContainerSpecs(&apiv1.Container{
 							Name:                   gp.env.Metadata.Name,
 							Image:                  gp.env.Spec.Runtime.Image,
 							ImagePullPolicy:        gp.runtimeImagePullPolicy,
@@ -560,7 +560,7 @@ func (gp *GenericPool) createPool() error {
 									},
 								},
 							},
-						},
+						}, gp.env.Spec.Runtime.Container),
 						{
 							Name:                   "fetcher",
 							Image:                  gp.fetcherImage,