Add advisory lock before creating label in create/merge operation

[mdianjun]

When merging nodes or edges concurrently, there is label with the same name created by different session.
However, checking whether the label exists cannot be guaranteed consistency. This commit add an advisory lock
to ensure creating label is serial.

[mdianjun]

@MuhammadTahaNaveed PTAL, thanks.

[jrgemignani]

@MuhammadTahaNaveed Can you check if this is a new CI issue?

[jrgemignani]

@mdianjun Can you rebase (against the master) and force push this PR? We had to fix the CI that was causing build issues.

[mdianjun]

@mdianjun Can you rebase (against the master) and force push this PR? We had to fix the CI that was causing build issues.

Have rebased it.

[jrgemignani]

When merging nodes or edges concurrently, there is label with the same name created by different session. However, checking whether the label exists cannot be guaranteed consistency. This commit add an advisory lock to ensure creating label is serial.

@mdianjun As this fixes a purported issue, can you provide an example showing this issue? Additionally, can you provide regression tests for it?

edit: Why only merge and not create?

[mdianjun]

@mdianjun As this fixes a purported issue, can you provide an example showing this issue? Additionally, can you provide regression tests for it?

edit: Why only merge and not create?

@jrgemignani Create operation should be fixed as well, I missed it. I add a python script in regress test.

[jrgemignani]

@MuhammadTahaNaveed Is this something we need to add/fix? Or,...