Fixing an empty var val for the mnaio build.sh

It looks like bash was throwing single qoutes around the variable
  default if the var was empty causing ansible to think it is the
  play.  Thanks to Matt Thompson's help, we pulled that out into
  a separate export to remove the single quotes.

Change-Id: Id04f840871f3371cf8258a8135536d37738e4e12
Closes-Bug: 1752357

multi-node-aio/build.sh

@@ -24,6 +24,8 @@ ansible mnaio_hosts \
         -m pip \
         -a "name=netaddr"
 
+export MNAIO_ANSIBLE_PARAMETERS=${MNAIO_ANSIBLE_PARAMETERS:-""}
+
 ansible-playbook -vv \
                  -i ${MNAIO_INVENTORY:-"playbooks/inventory"} \
                  -e setup_host=${SETUP_HOST:-"true"} \
@@ -51,7 +53,6 @@ ansible-playbook -vv \
                  -e swift_vm_server_ram=${SWIFT_VM_SERVER_RAM:-"1024"} \
                  -e container_tech=${CONTAINER_TECH:-"lxc"} \
                  -e ipxe_kernel_url=${IPXE_KERNEL_URL:-"http://boot.ipxe.org/ipxe.lkrn"} \
-                 -e ipxe_path_url=${IPXE_PATH_URL:-""} \
-                 ${MNAIO_ANSIBLE_PARAMETERS:-""} \
+                 -e ipxe_path_url=${IPXE_PATH_URL:-""} ${MNAIO_ANSIBLE_PARAMETERS} \
                  --force-handlers \
                  playbooks/site.yml