refine startup alerts, reversions in mocks

ui/src/app/guards/maintenance.guard.ts

@@ -1,6 +1,5 @@
 import { Injectable } from '@angular/core'
 import { CanActivate, Router, CanActivateChild } from '@angular/router'
-import { tap } from 'rxjs/operators'
 import { ServerStatus } from '../services/patch-db/data-model'
 import { PatchDbService } from '../services/patch-db/patch-db.service'
 

ui/src/app/guards/unmaintenance.guard.ts

@@ -14,8 +14,8 @@ export class UnmaintenanceGuard implements CanActivate {
     private readonly router: Router,
     private readonly patch: PatchDbService,
   ) {
-    this.patch.sequence$.subscribe(_ => {
-      this.serverStatus = this.patch.data['server-info'].status
+    this.patch.watch$('server-info', 'status').subscribe(status => {
+      this.serverStatus = status
     })
   }