Read pg_control file only when --check option is enabled in restore

[egashira-yusuke]

This is correction for #114, the second version patch based on discussion in #119 .
The target is PostgreSQL 11 and later.

In restore processing, pg_rman always had read the pg_control file from target database cluster.
However, if the database cluster had been deleted completely, pg_rman restore was failed because of calling get_controlfile().
The information of pg_control file in old database cluster is used only by --check option.
It is not necessarily required for database restore.

This patch modify to read pg_control file only when --check option is enabled in restore process.
Also, this introduce file existence check.
If --check option is specified and pg_control file is not found in restore process, pg_rman reports ERROR and interrupts processing.

[amitlan]

Moon-san, Egashira-san,

This seems OK, thanks. I understand that this PR is meant as correction for already merged PR #119

Please push this change to the following branches: master, 12, 10, 9.6, 9.5, 9.4

Maybe you'll need to combine #119 and this PR when pushing to other branches, because #119 was only merged with 11.

[MoonInsung]

Moon-san, Egashira-san,

This seems OK, thanks. I understand that this PR is meant as correction for already merged PR #119

Please push this change to the following branches: master, 12, 10, 9.6, 9.5, 9.4

Maybe you'll need to combine #119 and this PR when pushing to other branches, because #119 was only merged with 11.

Dear Amit.

Thank you!
I will merge it. And I will commit for each branches!

Best regards.
Moon.

[egashira-yusuke]

Amit-san, Moon-san,

Thank you for reviewing and merging!

Please push this change to the following branches: master, 12, 10, 9.6, 9.5, 9.4

I think that it is not nessesary for 10, 9.6, 9.5 branches.
In 10, 9.6 and 9.5 branches, pg_rman seems not to use the value from pg_control for calculating WAL segment size in restore with --check.
So, I think this correction should be pushed to master and 12 branches.

[MoonInsung]

Amit-san, Moon-san,

Thank you for reviewing and merging!

Please push this change to the following branches: master, 12, 10, 9.6, 9.5, 9.4

I think that it is not nessesary for 10, 9.6, 9.5 branches.
In 10, 9.6 and 9.5 branches, pg_rman seems not to use the value from pg_control for calculating WAL segment size in restore with --check.
So, I think this correction should be pushed to master and 12 branches.

Dear egashira-yusuke-san.

I'm sorry. my mistake pressed the close button....
It is open again and I will do the merge soon.
And like your opinion, make sure to I will commit after investigating the each branchs where the actual merge needs to proceed.
Thank you!

Best regards.
Moon.