LU-1538 tests: standardize test script init - dne-part-2

Standardize the initial Lustre test script initialization for
clarity and consistency for test suites in review-dne-part-2.

The LUSTRE path is already normalized in init_test_env(), so
this doesn't need to be done in the caller.  Use $(...)
subshells instead of `...` in the affected lines.  Remove
NAME, CHECKSTAT, TMP, SAVE_PWD,SRCDIR, PATH, MULTIOP, SETUP,
CLEANUP variable initialization, since it is already done in
init_test_env() or not needed in the test script.  Remove all
calls to get_lustre_env() in the test scripts since this is
called in init_test_env().

Move all definitions of ALWAYS_EXCEPT and SLOW to after
init_test_env() and init_logging() and call build_test_filter()
immediately after the ALWAYS_EXCEPT and SLOW definitions.

Test-Parameters: trivial
Test-Parameters: testgroup=review-dne-part-2
Signed-off-by: James Nunez <jnunez@whamcloud.com>
Change-Id: I6a04c9ffc0ce965c7f170119814d6ee8a30631df
Reviewed-on: https://review.whamcloud.com/35787
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Emoly Liu <emoly@whamcloud.com>
Reviewed-by: Wei Liu <sarah@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>