test/rcu: make global variable per core

test/rcu: make global variable per core

Each hash entry has a pointer to one uint32 memory location.
However, all the readers increment the same location causing
race conditions. Allocate memory for each thread so that each
thread will increment its own memory location.

Fixes: b87089b0bb19 ("test/rcu: add API and functional tests")
Cc: stable@dpdk.org
Reported-by: David Marchand <david.marchand@redhat.com>
Signed-off-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Tested-by: David Marchand <david.marchand@redhat.com>