feat(xen-api/objects): buffer objects' events on initial fetch (#3994)

XO requires all objects to be available at the same time.

packages/xen-api/src/index.js

@@ -983,6 +983,8 @@ export class Xapi extends EventEmitter {
     const types = this._watchedTypes || this._types
 
     // initial fetch
+    const flush = this.objects.bufferEvents()
+    try {
       await Promise.all(
         types.map(async type => {
           try {
@@ -1002,6 +1004,9 @@ export class Xapi extends EventEmitter {
           }
         })
       )
+    } finally {
+      flush()
+    }
     this._resolveObjectsFetched()
 
     // event loop
@@ -1060,7 +1065,9 @@ export class Xapi extends EventEmitter {
   // It also has to manually get all objects first.
   _watchEventsLegacy() {
     const getAllObjects = async () => {
-      return Promise.all(
+      const flush = this.objects.bufferEvents()
+      try {
+        await Promise.all(
           this._types.map(type =>
             this._sessionCall(`${type}.get_all_records`).then(
               objects => {
@@ -1075,7 +1082,11 @@ export class Xapi extends EventEmitter {
               }
             )
           )
-      ).then(() => this._resolveObjectsFetched())
+        )
+      } finally {
+        flush()
+      }
+      this._resolveObjectsFetched()
     }
 
     const watchEvents = () =>