Replace @SHELL@ with /bin/sh in condense_test scripts

This MR fixes the shebang line of the condense test scripts which are run on the dmt test nodes to reduce the disk space used by the trigger and segment (xml) files by tarring and removing directories that are older than a specified age.

aLigo/scripts/condense_test_LHO

-#! @SHELL@
+#! /bin/sh
 #  Segment save time - the number of 100k second directories to leave as 
 #  uncompressed xml files. The default is was changed from 100 to 20 to 
 #  fit in the reduced space available on thezfs filesystems.