should check volume-name format while mapping nbd about curveadm HOT 3 CLOSED

https://github.com/opencurve/curveadm/wiki/curvebs-client-deployment#%E7%AC%AC-3-%E6%AD%A5%E6%98%A0%E5%B0%84-curvebs-%E5%8D%B7

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$ curveadm map <user>:<volume-name> -c client.yaml --create --size 10GB <volume-name> must be start with '/' , but many users ignored it even we describe this note in manual.

so I think we should add some checks about the format of <volume-name>, such as if it is not start with '/', we print some error messages to users to suggest them using correct format.

agree!

PS：I think we should also check volume owner which can not be root user.

from curveadm.

after this change the prompt message is like this:

hzwangpan@pubbeta2-curve101:~$ ./curveadm map wp:vol2 -c client.yaml --create --size 1000GB
Error: invalid volume format, image name must start with /

from curveadm.