Bug 1194529 - Revert to the previous value of the TEST_ONLY_REAUTH pref instead of clearing it after receiving the notification. r=MattN

This was causing subsequent tests to fail when a pref was set via browser.ini.

Differential Revision: https://phabricator.services.mozilla.com/D61750

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

browser/modules/test/OSKeyStoreTestUtils.jsm

@@ -45,6 +45,7 @@ var OSKeyStoreTestUtils = {
   async waitForOSKeyStoreLogin(login = false) {
     const str = login ? "pass" : "cancel";
 
+    let prevValue = Services.prefs.getStringPref(this.TEST_ONLY_REAUTH, "");
     Services.prefs.setStringPref(this.TEST_ONLY_REAUTH, str);
 
     await TestUtils.topicObserved(
@@ -52,6 +53,6 @@ var OSKeyStoreTestUtils = {
       (subject, data) => data == str
     );
 
-    Services.prefs.setStringPref(this.TEST_ONLY_REAUTH, "");
+    Services.prefs.setStringPref(this.TEST_ONLY_REAUTH, prevValue);
   },
 };