_rebase_relative_time_on_now() is used both by _address_get_lifetime()/nm_platform_ip[46]_address_sync()
and the to_string() functions.

In the latter case, we want to print the original value, without padding. Otherwise in
the addresses are printed in the logs with an additional 5 seconds
padding, which is confusing.

For adding addresses in platform however, we still want to keep the
padding. So pass it on as additional parameter.

Signed-off-by: Thomas Haller <thaller@redhat.com>