dbutil: Update dump cmd.

This commit updates the dump command so that it works with all of the
user database implemenations. It also simplifies the implementation to
only allow for dumping a single user to stdout. There is no use case
that requires dumping all of the users at once. The migrate command
should be used when migrating databases, not the dump command.

politeiawww/cmd/politeiawww_dbutil/politeiawww_dbutil.go

@@ -155,7 +155,7 @@ const usageMsg = `politeiawww_dbutil usage:
           CockroachDB args : <importDir>
     -dump
           Dump the entire database or the contents of a specific user
-          Required DB flag : -leveldb
+          Required DB flag : -leveldb or -cockroachdb or -mysql
           LevelDB args     : <username>
     -createkey
           Create a new encryption key that can be used to encrypt data at rest
@@ -179,28 +179,19 @@ const usageMsg = `politeiawww_dbutil usage:
           CockroachDB args : <username>`
 
 func cmdDump() error {
-	// If email is provided, only dump that user.
 	args := flag.Args()
-	if len(args) == 1 {
-		username := args[0]
-		u, err := userDB.UserGetByUsername(username)
-
-		if err != nil {
-			return err
-		}
-
-		fmt.Printf("Key    : %v\n", username)
-		fmt.Printf("Record : %v", spew.Sdump(u))
-		return nil
+	if len(args) == 0 {
+		return fmt.Errorf("username was not provided")
 	}
 
-	err := userDB.AllUsers(func(u *user.User) {
-		fmt.Printf("Key    : %v\n", u.Username)
-		fmt.Printf("Record : %v\n", spew.Sdump(u))
-	})
+	username := args[0]
+	u, err := userDB.UserGetByUsername(username)
 	if err != nil {
 		return err
 	}
+
+	fmt.Printf("%v", spew.Sdump(u))
+
 	return nil
 }
 
@@ -863,18 +854,12 @@ func _main() error {
 	}
 
 	switch {
-	case *addCredits || *setAdmin || *stubUsers || *resetTotp:
+	case *addCredits || *setAdmin || *stubUsers || *resetTotp || *dump:
 		// These commands must be run with -cockroachdb, -mysql or -leveldb.
 		if !*level && !*cockroach && !*mysql {
 			return fmt.Errorf("missing database flag; must use " +
 				"-leveldb, -cockroachdb or -mysql")
 		}
-	case *dump:
-		// These commands must be run with -leveldb.
-		if !*level {
-			return fmt.Errorf("missing database flag; must use " +
-				"-leveldb with this command")
-		}
 	case *verifyIdentities, *setEmail:
 		// These commands must be run with either -cockroachdb or -mysql.
 		if !*cockroach && !*mysql {