Michael Kuhn 94acd8f235 cmd/load: Fix usage output (#15180) ...

args.specs is a list, which results in output like this:
```
eval `spack load --sh ['libxml2', 'xz']`
```

We want this instead:
```
eval `spack load --sh libxml2 xz`
```

2020-02-24 09:46:41 -06:00

..

spack

cmd/load: Fix usage output (#15180)

2020-02-24 09:46:41 -06:00