When RUN returns with a non-zero return code it prints the command
that was executed as a Go []string:
```
INFO[0000] The command &{[/bin/sh -c noop a1 a2]} returned a non-zero code: 127
```
instead it should look like this:
```
INFO[0000] The command "/bin/sh -c noop a1 a2" returned a non-zero code: 127
```
Signed-off-by: Doug Davis <dug@us.ibm.com>
54662eae10