stats: memory leak in stat_validate_counter_vector
stats: memory leak in stat_validate_counter_vector

Free the existing vectors prior to losing them.

Type: fix
Ticket: VPPSUPP-94

Signed-off-by: Steven Luong <a748ea44ad7b179c2313a856d44e1e4eb39869bb@cisco.com>
Change-Id: Ic15f1fbc7a0c6c348065fc9759ee5d5c43013b91
Signed-off-by: Ole Troan <aeed71d78dc09e4764ceac69b111eee9b50cfdd0@cisco.com>

chrisy/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,FDio/vpp,chrisy/vpp,chrisy/vpp,FDio/vpp,FDio/vpp,FDio/vpp,chrisy/vpp