IO/Image: Fix TestSetFileNames to glob only numeric suffixes

Teach IO/Image/Testing/(Python|Tcl)/TestSetFileNames.(py|tcl) to glob
only Data/headsq/quarter.* files ending in a digit.  This will avoid
picking up ".<algo>-stamp" files created by the ExternalData module.

Change-Id: Ieb145f1d41edbcce7e57355b485baf2dd8b4b9ee
Merge topic 'TestSetFileNames-glob-numbers' into master

7b3f3da0 IO/Image: Fix TestSetFileNames to glob only numeric suffixes