This change introduces capability to customize internal-client.conf,
which is used by several daemon processes like container-sharder.
Backport note:
Replaced swift::params::user by the hard-coded user name because
f781eb9e34 is present only in yoga and
later.
Closes-Bug: #1986599
Related-Bug: #1921319
Change-Id: I200e3a4ff323a07778ec6c4d7dd96824c72a12cf
(cherry picked from commit efcef86de7)
(cherry picked from commit ab3cf92d79)
(cherry picked from commit b5cb280779)