Replace deprecated package dependencies

[kishen-v]

What happened: The following packages have been deprecated:

• [x] github.com/golang/mock/mockgen@v1.6.0 - A maintained fork of the same is available through go.uber.org/mock/gomock
• [x] io/ioutil - Same funcitonalities are available in packages - io or os.

What you expected to happen:

How to reproduce it (as minimally and precisely as possible):

Anything else we need to know?:

Environment:

• pvsadm version (use pvsadm version):
• Environment - On-Prem or IBM PowerVS:
• OS (e.g: cat /etc/os-release):
• Kernel (e.g. uname -a):
• Others:

[kishen-v]

/assign

[kishen-v]

Raised PR for the first task: https://github.com/ppc64le-cloud/pvsadm/pull/537

[kishen-v]

PR for task 2: https://github.com/ppc64le-cloud/pvsadm/pull/538