LU-15358 tests: fix check in sanityn test_80b

LU-15358 tests: fix check in sanityn test_80b

Shellcheck found checks in sanityn test_80b using bad logic:

        [ $rc -ne 0 -o $rc -ne 16 ] || {
                echo "touch file failed with $rc1"
                break;
        }

This can never be false, so the subtest will never detect errors.
Fix these checks, along with some related style issues.

Test-Parameters: trivial testlist=sanityn mdscount=2 mdtcount=4 env=ONLY=80,ONLY_REPEAT=50
Fixes: 220e6cbfa65c5 ("LU-6475 mdt: race between open and migrate")
Signed-off-by: Andreas Dilger <adilger@whamcloud.com>
Change-Id: I541fe6f3ae253ea1c4d7fa2bcfad9052e374e60c
Reviewed-on: https://review.whamcloud.com/46706
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Reviewed-by: Lai Siyao <lai.siyao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>