Update in-use label and location picker behavior

[lesleyjanenorton]

Here we:

• Remove the "in-use" label from vpn-card (FXVPN-169)
• Add an "in-use" label to the location picker button that is
  • visible when a site-specific location setting is not in effect
  • hidden when the site is excluded
  • disable the location picker button when the site is excluded (FXVPN-167)
• Makes some opportunistic UI tweaks

[strseb]

I thought "in use" should still be on the card when using the default location?
but anyway lgtm

[lesleyjanenorton]

I thought "in use" should still be on the card when using the default location?
but anyway lgtm

@strseb Santiago changed the behavior yesterday after thinking about it some more