MM-62079: Fix permissions being reset properly (#29574)

The default role permissions weren't being saved
to a separate variable which would have not restored
them properly. This was a problem in various other
tests, potentially causing side-effects in other
flaky tests as well.

We fix that, as well as clean up the for loop
a bit and mention how many messages were recieved
in the failure message so that it becomes clear
whether no messages were recieved, or atleast some
were received.

https://mattermost.atlassian.net/browse/MM-62079
```release-note
NONE
```

server/channels/api4/user_viewmembers_test.go

@@ -120,7 +120,8 @@ func TestAPIRestrictedViewMembers(t *testing.T) {
 				"api.context.permissions.app_error",
 			},
 		}
-		defer th.RestoreDefaultRolePermissions(th.SaveDefaultRolePermissions())
+		defaultPerms := th.SaveDefaultRolePermissions()
+		defer th.RestoreDefaultRolePermissions(defaultPerms)
 
 		for _, tc := range testCases {
 			t.Run(tc.Name, func(t *testing.T) {
@@ -201,7 +202,8 @@ func TestAPIRestrictedViewMembers(t *testing.T) {
 				"api.context.permissions.app_error",
 			},
 		}
-		defer th.RestoreDefaultRolePermissions(th.SaveDefaultRolePermissions())
+		defaultPerms := th.SaveDefaultRolePermissions()
+		defer th.RestoreDefaultRolePermissions(defaultPerms)
 
 		for _, tc := range testCases {
 			t.Run(tc.Name, func(t *testing.T) {
@@ -282,7 +284,8 @@ func TestAPIRestrictedViewMembers(t *testing.T) {
 				"api.context.permissions.app_error",
 			},
 		}
-		defer th.RestoreDefaultRolePermissions(th.SaveDefaultRolePermissions())
+		defaultPerms := th.SaveDefaultRolePermissions()
+		defer th.RestoreDefaultRolePermissions(defaultPerms)
 
 		for _, tc := range testCases {
 			t.Run(tc.Name, func(t *testing.T) {
@@ -363,7 +366,8 @@ func TestAPIRestrictedViewMembers(t *testing.T) {
 				"api.context.permissions.app_error",
 			},
 		}
-		defer th.RestoreDefaultRolePermissions(th.SaveDefaultRolePermissions())
+		defaultPerms := th.SaveDefaultRolePermissions()
+		defer th.RestoreDefaultRolePermissions(defaultPerms)
 
 		for _, tc := range testCases {
 			t.Run(tc.Name, func(t *testing.T) {
@@ -444,7 +448,8 @@ func TestAPIRestrictedViewMembers(t *testing.T) {
 				"api.context.permissions.app_error",
 			},
 		}
-		defer th.RestoreDefaultRolePermissions(th.SaveDefaultRolePermissions())
+		defaultPerms := th.SaveDefaultRolePermissions()
+		defer th.RestoreDefaultRolePermissions(defaultPerms)
 
 		for _, tc := range testCases {
 			t.Run(tc.Name, func(t *testing.T) {