Changed sql_mode to be set with an array of options rather than a string (10.4.x)
requested to merge issue/drupal-2939760:2939760-10.4-allow-granular-overriding-of-sqlmode-options into 10.4.x
Changed sql_mode to be set with an array of options rather than a string. Backport of 2939760 from 11.x branch.
Closes #2939760