Fix S1003 violations and drop suppression

nogo.yaml

@@ -239,10 +239,6 @@ analyzers:
         # See above.
         - "symbol \"runtime_pollWaitCanceled\".*"
         - "symbol \"runtime_procPin\".*"
-  S1003: # Replace index+len check with strings.Contains
-    # disabled for now due to existing violations.
-    internal:
-      exclude: [".*"]
   S1004: # Simplify bytes.Compare(...) != 0 into bytes.Equal(...)
     # disabled for now due to existing violations.
     internal:

pkg/sentry/vfs/filesystem_type.go

@@ -112,7 +112,7 @@ func (vfs *VirtualFilesystem) getFilesystemType(name string) *registeredFilesyst
 	fsname := name
 	// Fetch a meaningful part of name if there is a dot in the name
 	// and use left part of a string as fname.
-	if strings.Index(name, ".") != -1 {
+	if strings.Contains(name, ".") {
 		fsname = strings.Split(name, ".")[0]
 	}
 	return vfs.fsTypes[fsname]