[Persistence] Use identifier service to get key

Retrieve key from identifier service for all persist operations.

Fixes https://github.com/nasa/openmct/issues/1013

platform/core/src/capabilities/PersistenceCapability.js

@@ -60,11 +60,6 @@ define(
             this.$q = $q;
         }
 
-        function getKey(id) {
-            var parts = id.split(":");
-            return parts.length > 1 ? parts.slice(1).join(":") : id;
-        }
-
         /**
          * Checks if the value returned is falsey, and if so returns a
          * rejected promise
@@ -131,7 +126,7 @@ define(
             // ...and persist
             return persistenceFn.apply(persistenceService, [
                 this.getSpace(),
-                getKey(domainObject.getId()),
+                this.getKey(),
                 domainObject.getModel()
             ]).then(function (result) {
                 return rejectIfFalsey(result, self.$q);
@@ -159,7 +154,7 @@ define(
 
             return this.persistenceService.readObject(
                     this.getSpace(),
-                    this.domainObject.getId()
+                    this.getKey()
                 ).then(updateModel);
         };
 
@@ -178,6 +173,17 @@ define(
             return this.identifierService.parse(id).getSpace();
         };
 
+
+        /**
+         * Get the key for this domain object in the given space.
+         *
+         * @returns {string} the key of the object in it's space.
+         */
+        PersistenceCapability.prototype.getKey = function () {
+            var id = this.domainObject.getId();
+            return this.identifierService.parse(id).getKey();
+        };
+
         return PersistenceCapability;
     }
 );

platform/core/test/capabilities/PersistenceCapabilitySpec.js

@@ -101,6 +101,7 @@ define(
                 });
                 mockIdentifierService.parse.andReturn(mockIdentifier);
                 mockIdentifier.getSpace.andReturn(SPACE);
+                mockIdentifier.getKey.andReturn(id);
                 persistence = new PersistenceCapability(
                     mockCacheService,
                     mockPersistenceService,