HPCC-8514 Fix ESDL parameter defaults not being set properly

A regression in version 3.10 due to refactoring of parameter code
meant that ESDL defined default values were not always being set
properly.  Only 1 small related issue has been reported, so this
change should probably be targeted for 3.10.2 where it can be
properly tested before release.

Signed-off-by: Anthony Fishbeck <Anthony.Fishbeck@lexisnexis.com>