In the previous commit 8958cecad6
the default ports (80/443) were removed for both the `scrapeURL` and
`instance` label values for those targets without a port in
`__address__`. Different values in the `instance` label generate new
time series.
This commit reverts the changes made to the `instance` label. Now,
for those targets:
- `scrapeURL` will remain unchanged.
- The `instance` label value will include the default port.
https://github.com/VictoriaMetrics/VictoriaMetrics/issues/6792
(cherry picked from commit e97e966f82)
5b49fd83be