Ensure approvals store is only initialized once.

app/assets/javascripts/merge_request_widget/approvals/components/approvals_body.js.es6

@@ -33,7 +33,7 @@
       },
     },
     beforeCreate() {
-      return gl.ApprovalsStore.fetch().then();
+      return gl.ApprovalsStore.initStoreOnce();
     },
     template: `
       <div>

app/assets/javascripts/merge_request_widget/approvals/components/approvals_footer.js.es6

@@ -20,7 +20,7 @@
       },
     },
     beforeCreate() {
-      return gl.ApprovalsStore.fetch();
+      return gl.ApprovalsStore.initStoreOnce();
     },
     template: `
       <div v-if='hasApprovers' class='mr-widget-footer approved-by-users approvals-footer clearfix'>

app/assets/javascripts/merge_request_widget/approvals/stores/approvals_store.js.es6

@@ -15,12 +15,32 @@
     init(rootStore) {
       this.rootStore = rootStore;
       this.api = new gl.ApprovalsApi(rootStore.dataset.endpoint);
+      this.state = {
+        loading: false,
+        loaded: false,
+      };
     }
 
     assignToRootStore(data) {
       return this.rootStore.assignToData('approvals', data);
     }
 
+    initStoreOnce() {
+      const state = this.state;
+      if (state.loading || state.loaded) {
+        state.loading = true;
+        this.fetch()
+          .then(() => {
+            state.loading = false;
+            state.loaded = true;
+          })
+          .catch((err) => {
+            console.error(`Failed to initialize approvals store: ${err}`);
+          });
+      }
+      return this.fetch();
+    }
+
     fetch() {
       return this.api.fetchApprovals()
         .then(res => this.assignToRootStore(res.data));