Add -exp to end of Experimental build names (trilinos#2933)

This is needed in order to ensure that the Experimental builds don't have the
same site and build name as builds going to the other Nightly CDash groups
that ATDM Trilinos groups go to.  Simply using the real 'hostname' for the
CDash build site name is not enough because for 'mutrino' the 'hostname'
actually is 'mutrino'!  Therefore, we need to add '-exp' to account for this
on machines where the CDash site name is the same as the 'hostname'.

cmake/ctest/drivers/atdm/TrilinosCTestDriverCore.atdm.cmake

@@ -146,6 +146,7 @@ MACRO(TRILINOS_SYSTEM_SPECIFIC_CTEST_DRIVER)
     # "Experimental" builds with the same 'site' and 'buildname' as builds in
     # the "Specialized" and "ATDM" groups.
     SET(CTEST_SITE "$ENV{ATDM_CONFIG_REAL_HOSTNAME}")
+    SET(CTEST_BUILD_NAME "$ENV{JOB_NAME}-exp")
   ELSE()
     # For regular builds ("Specialized" and "ATDM"), set the CDash site name
     # so that it does not change depending on what node on a given machine