Necessary changes if one of the test scripts is to be used with a RPM installation (bug#17194).

This change handles finding the server and the other programs,
but it does not solve the problem to get a writable "var" directory.
If we want to avoid world-writable directories below "/usr/share/mysql-test" (and we do!), 
any automatic solution would require fixed decisions which may not match the local installation.

For the Perl script, use "--vardir"; for the shell script, create "mysql-test/var" manually.


mysql-test/mysql-test-run.pl:
  Modifications to use this script in a RPM installation (bug#17194):
  - The tests are one level further down, "/usr/share/mysqltest" (vs. "/usr/bin").
  - A "mysql-bench" might not exist.
  - "mysql-test" is owned by root and not world-writable, so "var" must be put somewhere else.
  - The server, "mysqld", is in a different location, "/usr/sbin".
  
  Note that the "--vardir" option must be used in a RPM installation,
  unless "mysql-test" is made writable for the user who runs the tests (not done automatically).
mysql-test/mysql-test-run.sh:
  Necessary changes if this script is to be used with a RPM installation (bug#17194):
  - The tests are one level further down, "/usr/share/mysqltest" (vs. "/usr/bin").
  - The server, "mysqld", is in a different location, "/usr/sbin".
  
  Note that these changes are not sufficient, as the user needs a writable "mysql-test/var" subdirectory.
  Either this is created manually, or the script can not be used.
  An alternative is the corresponding Perl script which supports a "--vardir" option.