LU-15931 tests: Escape * in log()

LU-15931 tests: Escape * in log()

So it does not print every file name in test description in dmesg

Test-Parameters: trivial testlist=sanity env=ONLY=160s
Fixes: f60b307c50 ("LU-14699 mdd: proactive changelog garbage collection")
Signed-off-by: Oleg Drokin <green@whamcloud.com>
Change-Id: I300fde0f71ef15a5c6573a67324944ba8d53f8e3
Reviewed-on: https://review.whamcloud.com/47597
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>