config-vm: Recycle the hook-process schema

We already have two ways to specify a process to launch (for the
container process and for hooks).  This commit recycles the
hook-process schema for launching the hypervisor.  I prefer using the
more-fundamental container process schema, but Michael felt it had too
many properties that wouldn't apply to the hypervisor-launching case
[1].

[1]: opencontainers#949 (comment)

Signed-off-by: W. Trevor King <wking@tremily.us>

config-vm.md

@@ -5,17 +5,14 @@ The virtual-machine container specification provides additional configuration fo
 
 ## <a name="HypervisorObject" /> Hypervisor Object
 
-**`hypervisor`** (object, OPTIONAL) specifies details of the hypervisor that manages the container virtual machine.
-* **`path`** (string, REQUIRED) path to the hypervisor binary that manages the container virtual machine.
-    This value MUST be an absolute path in the [runtime mount namespace](glossary.md#runtime-namespace).
-* **`parameters`** (array of strings, OPTIONAL) specifies an array of parameters to pass to the hypervisor.
+**`hypervisor`** (object, OPTIONAL) configures the hypervisor process using the [hook-process schema](config.md#hook-process).
 
 ### Example
 
 ```json
     "hypervisor": {
         "path": "/path/to/vmm",
-        "parameters": ["opts1=foo", "opts2=bar"]
+        "args": ["vmm", "opts1=foo", "opts2=bar"]
     }
 ```
 

schema/config-vm.json

@@ -7,19 +7,7 @@
         ],
         "properties": {
             "hypervisor": {
-                "description": "hypervisor config used by VM-based containers",
-                "type": "object",
-                "required": [
-                    "path"
-                ],
-                "properties": {
-                    "path": {
-                        "$ref": "defs.json#/definitions/FilePath"
-                    },
-                    "parameters": {
-                        "$ref": "defs.json#/definitions/ArrayOfStrings"
-                    }
-                }
+                "$ref": "defs.json#/definitions/Hook"
             },
             "kernel": {
                 "description": "kernel config used by VM-based containers",

specs-go/config.go

@@ -504,21 +504,13 @@ type WindowsHyperV struct {
 // VM contains information for virtual-machine-based containers.
 type VM struct {
 	// Hypervisor specifies hypervisor-related configuration for virtual-machine-based containers.
-	Hypervisor VMHypervisor `json:"hypervisor,omitempty"`
+	Hypervisor *Hook `json:"hypervisor,omitempty"`
 	// Kernel specifies kernel-related configuration for virtual-machine-based containers.
 	Kernel VMKernel `json:"kernel"`
 	// Image specifies guest image related configuration for virtual-machine-based containers.
 	Image VMImage `json:"image,omitempty"`
 }
 
-// VMHypervisor contains information about the hypervisor to use for a virtual machine.
-type VMHypervisor struct {
-	// Path is the host path to the hypervisor used to manage the virtual machine.
-	Path string `json:"path"`
-	// Parameters specifies parameters to pass to the hypervisor.
-	Parameters string `json:"parameters,omitempty"`
-}
-
 // VMKernel contains information about the kernel to use for a virtual machine.
 type VMKernel struct {
 	// Path is the host path to the kernel used to boot the virtual machine.