test: fix global variable multiple definitions

test: fix global variable multiple definitions

Multiple global variable are defined in multiple unit test files with
same name, but all unit test files are linked into single executable,
which means those variables share same storage which is not the
intention, fixed by making global variables 'static'.

Issue has been detected by '-fno-common' gcc flag.

Fixes: fdeb30fa7102 ("test/bitrate: add unit tests for bitrate library")
Fixes: c3eabff124e6 ("distributor: add unit tests")
Fixes: 0e925aef2779 ("app/test: add EFD functional and perf tests")
Fixes: 359e17bf081f ("app/test: improve hash unit tests")
Fixes: c7eb0972e74b ("test/hash: add lock-free r/w concurrency")
Fixes: 1e3676a06e4c ("test/latency: add unit tests for latencystats library")
Fixes: 0cc67a96e486 ("test/member: add functional and perf tests")
Fixes: e6a14121f4ae ("test/rcu: remove arbitrary limit on max core count")
Fixes: 104dbec2081a ("test/rcu: increase size of core numbers")
Cc: stable@dpdk.org
Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>