doc: Differentiate location meaning between host and server

Host location and server location have very different meanings in IPA.
ipahost uses 'location' as an optional hint to where the host may be
physically located, ipaserever uses location to identify which DNS
location the server is part of.

This change updates documentation to make attribute description more
clear. Surrounding text have been changed to match text style as used in
other plugins.

This patch is related to: https://github.com/freeipa/freeipa/pull/6840