LU-14707 tests: Bashify scripts for Ubuntu et. al.

LU-14707 tests: Bashify scripts for Ubuntu et. al.

Some scripts use bash-isms that are not present in
bourne (sh) or Ubuntu's default dash shell.

Be explicit and prefer bash

HPE-bug-id: LUS-8398
Signed-off-by: Shaun Tancheff <shaun.tancheff@hpe.com>
Change-Id: I02f742e9787e1811b422b619e00911ee52673262
Reviewed-on: https://review.whamcloud.com/43786
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>