Have mash_browser_tests recreate BackgroundServiceManager per test

testing/buildbot/filters/mash.browser_tests.filter

Index: testing/buildbot/filters/mash.browser_tests.filter
diff --git a/testing/buildbot/filters/mash.browser_tests.filter b/testing/buildbot/filters/mash.browser_tests.filter
index 4e9e3a3182bd8f9ae8aae8262a56091d9ebd35c3..18b7136e675e8633b4ece7661f4a94548785b03a 100644
--- a/testing/buildbot/filters/mash.browser_tests.filter
+++ b/testing/buildbot/filters/mash.browser_tests.filter
@@ -28,7 +28,6 @@ AppWindowApiTest.SetShapeNoPerm
 AppWindowApiTest.VisibleOnAllWorkspacesInStable
 BluetoothInternalsTest.Startup_BluetoothInternals
 BootstrapTest.CleanUpFailedUser
-BootstrapTest.PRE_CleanUpFailedUser
 BrowserDialogTest.Invoke
 BrowsingDataRemoverTransportSecurityStateBrowserTest.ClearTransportSecurityState
 CastSessionBrowserTest.CreateAndDestroy
@@ -48,8 +47,6 @@ ChromeServiceWorkerTest.CanShutDownWithRegisteredServiceWorker
 ChromeServiceWorkerTest.FailRegisterServiceWorkerWhenJSDisabled
 ChromeServiceWorkerTest.FallbackMainResourceRequestWhenJSDisabled
 ConstrainedWebDialogBrowserTest.ReleaseWebContents
-ContentVerifierPolicyTest.PRE_PolicyCorruptedOnStartup
-ContentVerifierPolicyTest.PolicyCorruptedOnStartup
 CreateNewFolder/FileManagerBrowserTest.Test/0
 CreateNewFolder/FileManagerBrowserTest.Test/1
 CreateNewFolder/FileManagerBrowserTest.Test/2
@@ -157,8 +154,6 @@ FormClassifierTest.kChangeFormWithTreePasswordFieldsHTML
 InstantProcessNavigationTest.ForkForNavigationsFromInstantProcess
 InstantProcessNavigationTest.ForkForNavigationsToSearchURLs
 MultiProfileFileManagerBrowserTest.BasicDownloads
-MultiProfileFileManagerBrowserTest.BasicDrive
-MultiProfileFileManagerBrowserTest.PRE_BasicDownloads
 OpenAudioFiles/FileManagerBrowserTest.Test/1
 OpenAudioFiles/FileManagerBrowserTest.Test/2
 OpenAudioFiles/FileManagerBrowserTest.Test/3