Fix apt_proxy/ntp/vagrant plugins manifests

bootstrapvz/plugins/apt_proxy/manifest-schema.json

@@ -21,9 +21,7 @@
 					},
 					"required": ["address", "port"]
 				}
-			},
-			"required": ["apt_proxy"]
+			}
 		}
-	},
-	"required": ["plugins"]
+	}
 }

bootstrapvz/plugins/ntp/manifest-schema.json

@@ -16,9 +16,7 @@
 						}
 					}
 				}
-			},
-			"required": ["ntp"]
+			}
 		}
-	},
-	"required": ["plugins"]
+	}
 }

bootstrapvz/plugins/vagrant/manifest-schema.json

@@ -23,9 +23,7 @@
 			"type": "object",
 			"properties": {
 				"vagrant": {
-					"type": "object",
-					"properties": {
-					}
+					"type": "object"
 				}
 			}
 		}