Bug 1845464 - Fix hostinfo.dat not getting updated. r=mkmelin

Differential Revision: https://phabricator.services.mozilla.com/D184560

--HG--
extra : moz-landing-system : lando

mailnews/news/src/NntpIncomingServer.jsm

@@ -512,6 +512,7 @@ class NntpIncomingServer extends MsgIncomingServer {
     this._subscribable.startPopulating(msgWindow, forceToServer, getOnlyNew);
     this._groups = [];
 
+    this._hostInfoLoaded = false;
     if (!forceToServer) {
       this._hostInfoLoaded = await this._loadHostInfo();
       if (this._hostInfoLoaded) {