LU-12823 tests: basetest to remove A-Z in test name

LU-12823 tests: basetest to remove A-Z in test name

this is required for bash5, otherwise test_mkdir() fails:
test-framework.sh: line 8640: 24A: value too great for
	 base (error token is "24A")

Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: Ic2ab4c1530099fbbb57d12f06fbdc761c251ce58
Reviewed-on: https://review.whamcloud.com/36322
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: James Nunez <jnunez@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>