debuginfod-client: Don't leak id/version with duplicate os-release entries

debuginfod-client: Don't leak id/version with duplicate os-release entries

Found by GCC14 -Wanalyzer-double-free.

If the os-release file would contain multiple ID or VERSION_ID entries
we would leak the originally parsed one. Fix by seeing whether id or
version is already set and ignore any future entries.

	* debuginfod/debuginfod-client.c (add_default_headers): Check
	whether id or version is already set before resetting them.

Signed-off-by: Mark Wielaard <mark@klomp.org>