app/testpmd: fix memory leaks after xstats errors
app/testpmd: fix memory leaks after xstats errors

Fixes memory leaks detected by Coverity. These are due to ephemeral
memory allocations not being freed when errors occur.

Coverity issue: 127348

Fixes: e2aae1c1ced9 ("ethdev: remove name from extended statistic fetch")

Signed-off-by: Remy Horton <34c343e92f0e27f7a8e26a1d8d2146ae7c7dd1a3@intel.com>

john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk,john-mcnamara-intel/dpdk