s4/torture: reproducer for kernel oplocks issue with streams

s4/torture: reproducer for kernel oplocks issue with streams

test_smb2_kernel_oplocks3() wouldn't have failed without the patches,
I'm just adding it to have at least one test that tests with 2
clients. All other tests use just one client.

test_smb2_kernel_oplocks4() is the reproducer.

Bug: https://bugzilla.samba.org/show_bug.cgi?id=12791

Signed-off-by: Ralph Boehme <slow@samba.org>
Reviewed-by: Richard Sharpe <realrichardsharpe@gmail.com>
(backported from commit a334fff8a8c779704ee04ae784024efb67a6e9c9)