The Process lines in systemctl status join argv with spaces, making
multi-word arguments ambiguous and empty arguments invisible.
Use quote_command_line() with SHELL_ESCAPE_EMPTY to retain argument
boundaries. Leave the formatted string NULL for an empty argv vector so
that strna() prints n/a. Cover whitespace, empty arguments and literal
dollar signs in TEST-26-SYSTEMCTL.
Fixes#43938.
(cherry picked from commit a83a0d2fc461091b16a699aeba07a82d71545c71)
Jonghyun An
6eb23d3526