memory field of the config file is broken

[saruman9]

Steps to reproduce the issue:

1. Set the memory field in the config file.
   $HOME/.minikube/config/config.json:

{
    "WantUpdateNotification": false,
    "cpus": 7,
    "disk-size": "300000",
    "driver": "kvm2",
    "memory": "12g"
}

2. minikube start

Full output of minikube start command used, if not already included:

😄  minikube v1.17.1 on Arch
✨  Using the kvm2 driver based on user configuration
👍  Starting control plane node minikube in cluster minikube
🔥  Creating kvm2 VM (CPUs=7, Memory=3900MB, Disk=300000MB) ...
🐳  Preparing Kubernetes v1.20.2 on Docker 20.10.2 ...
    ▪ Generating certificates and keys ...
    ▪ Booting up control plane ...
    ▪ Configuring RBAC rules ...
🔎  Verifying Kubernetes components...
🌟  Enabled addons: storage-provisioner, default-storageclass
🏄  Done! kubectl is now configured to use "minikube" cluster and "default" namespace by default

Similar issues: #9017, #9057.

[afbjorklund]

Confirm that only using the flags is working:

defaults

"Memory": 6000,
"CPUs": 2,
"DiskSize": 20000,

flags

--cpus 4 --memory 2g --disk-size 32g

"Memory": 2048,
"CPUs": 4,
"DiskSize": 32768,

config

- cpus: 4
- disk-size: 32g
- memory: 2g

"Memory": 6000,
"CPUs": 4,
"DiskSize": 32768,

So, something with "no existing cluster config was found, will generate one from the flags"

[afbjorklund]

The difference is in the "Flags().Changed":

		if cmd.Flags().Changed(memory) {
			var err error
			mem, err = pkgutil.CalculateSizeInMB(viper.GetString(memory))
			if err != nil {
				exit.Message(reason.Usage, "Generate unable to parse memory '{{.memory}}': {{.error}}", out.V{"memory": viper.GetString(memory), "error": err})
			}

		diskSize, err := pkgutil.CalculateSizeInMB(viper.GetString(humanReadableDiskSize))
		if err != nil {
			exit.Message(reason.Usage, "Generate unable to parse disk size '{{.diskSize}}': {{.error}}", out.V{"diskSize": viper.GetString(humanReadableDiskSize), "error": err})
		}

Apparently it does not respect the config.