test/vhost/common.sh: make fio bin variable local

Make the variable local, so that we don't unnecessarily
read it's value from base script in case it's defined.

Signed-off-by: Karol Latecki <karol.latecki@intel.com>
Change-Id: Ib4d95d3c67cfa8918c67f0b2642e9a3fe2ca3260
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/2558
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Mellanox Build Bot
Reviewed-by: Darek Stojaczyk <dariusz.stojaczyk@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>

test/vhost/common.sh

@@ -931,6 +931,7 @@ function vm_wait_for_boot() {
 function vm_start_fio_server() {
 	local OPTIND optchar
 	local readonly=''
+	local fio_bin=''
 	while getopts ':-:' optchar; do
 		case "$optchar" in
 			-)