alter tag with [default] not working.

[Qubutol]

Describe the bug (must be provided)

I using alter tag with [default],it’s still not working.

Your Environments (must be provided)

• OS: centos7
• nebula-2020.03.20-nightly.el7-5.x86_64

How To Reproduce(must be provided)

Steps to reproduce the behavior:

1. Step 1

create tag t2 (name string default "N/A", age int default -1);
INSERT VERTEX t2() VALUES 11:();
fetch prop on t2 11;

I got:

2. Step 2
and then,I execute:

ALTER tag t2 add (description string default "none");
fetch prop on t2 11

I got:

3. Step 3
exectue:

INSERT VERTEX t2() VALUES 11:()

give me a error message:

[ERROR (-8)]: `description' not exist default value

Expected behavior

t2.description have a default value .

[Shylock-Hg]

Same for edge.

[Shylock-Hg]

Alter don't write default value in graph and meta layer, fix it :)