Only show separator if command has usage text

[mikecluck]

What type of PR is this?

(REQUIRED)

• bug

What this PR does / why we need it:

(REQUIRED)

• help.go was changed so that if a command does not have usage information, it will not show a separator

When getting completions for commands, I was getting some confusing output:

$ wizard <tab>
bags     potions  spells   wands  --

To me, it looked like there should be a command named --. After adding usage to a couple of them, I realized what was going on

$ wizard <tab>
bags             -- Bags for holding things                                                                                                                                                                                                                                                         
potions  spells  --                                                                                                                                                                                                                                                                                 
wands            -- Tools for wielding magic   

Which still looks weird. The ones without any usage still get a -- separator. My change ensures that the -- is only shown if there is associated usage information.

$ wizard <tab>
bags     potions  spells   wands

$ wizard <tab>
bags     -- Bags for holding things
wands    -- Tools for wielding magic
potions  spells

Which issue(s) this PR fixes:

(REQUIRED)

N/A

Release Notes

(REQUIRED)

Removed redundant separator in shell completions

[dearchap]

Thanks @mikecluck