refs #15336 - use i18n variable names and plural form

[domcleal]

No description provided.

[dLobatog]

@domcleal Now it's missing the hostgroup count, sorry for missing the plural vs singular string when I merged it

[domcleal]

Yeah, I removed it for a couple of reasons:

a) Primarily - gettext don't have a translation function that can handle the combination of two plural words in the same string, as there would be four different strings.
b) The change was only relating to the disassociation of hosts which can only have one org/loc, while host groups are like any other resource with multiple associations, hence it's unclear that they must be reassociated anyway.

[dLobatog]

Merged as b0f8d18, thanks @domcleal!