"Database Update Required" gives error where Database in remote server

So, in my setup the database is in a separate server. I used to give minimum required permission to WordPress from remote server. It was working fine. Did not had any issue in any past update.

But while was updating from 4.1.4 to 4.2.1, all went fine, now stuck at “Database Update Required”.

Things I have done:

1) I increased allowed memory from wp-config to 1024MB.

2) Temporary I have given ALL PRIVILEGES to remote server where WP is hosted.

3) Restarted server and service after each new approach.

Still stuck.

Whats The Result?
1) Site frontend is up. Homepage and all other pages are opening fine.
2) Dashboard takes you to “Database Update Required” pages, and clicking “Update WordPress Database” will take long long time and will give server error 502. Site is still online, only Dashboard is not accessible.

Things to consider:
Its a NGiNX system for WordPress with php-fpm. And using MariaDB in remote DB.

Resource I have already checked
1) http://codex.wordpress.org/Upgrading_WordPress

2) https://wordpress.org/support/topic/database-update-required-4?

3) https://wordpress.org/support/topic/hanging-on-database-update-required

4) http://stackoverflow.com/questions/17308436/wordpress-error-database-update-required