work around Dejagnu failure on modern Tcl

work around Dejagnu failure on modern Tcl

Modern releases of Tcl (8.5 and later?) require use the special
procedure "unknown" to implement some autoloading functionality.
Dejagnu replaces "unknown" with its own definition, without chaining
to the original version of "unknown".  This causes "clock format
[clock seconds]" to fail while trying to load the "msgcat" Tcl
package.

Use "exec date" instead of "clock format [clock seconds]" to work
around this bug.

(Also needs pullup to 1.7.)

ticket: 6926
version_fixed: 1.8.5

git-svn-id: svn://anonsvn.mit.edu/krb5/branches/krb5-1-8@24999 dc483132-0cff-0310-8789-dd5450dbe970