LU-13444 tests: sanity to set PTLDEBUG

LU-13444 tests: sanity to set PTLDEBUG

otherwise any server remount reset full debug to the default
value different from full debug we want in sanity.

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I2b5c5a4d2a62d11f0327686b11f9ab8f16b47b4f
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/38194
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>