[bug] usage of "pouch volume create" is not right

[Letty5411]

Issue Description
The usage of "pouch volume create" is incorrect.

Describe what happened:

#pouch volume create -h
Create a pouch volume

Usage:
  pouch volume create [args] NAME [flags]

<snip>

Describe what you expected to happen:
According to the usage, the following CMD should succeed:

#pouch volume create -d local volume-1
ERRO[0000] boltdb: put key: : key required

But "--name" is required:

#pouch volume create --name=volume-2
Scope:
CreatedAt:
Driver:       local
Mountpoint:
Name:         volume-2

How to reproduce it (as minimally and precisely as possible):
1.
2.
3.

Anything else we need to know?:

Environment:

• pouch version (use pouch version):
• OS (e.g. from /etc/os-release):
• Kernel (e.g. uname -a):
• Install tools:
• Others:

[Letty5411]

@rudyfly