Update -z with -a for --availability-zone as -z already used for local-mode  - Fix server list error when format is json.
Update -z with -a for --availability-zone as -z already used for local-mode
 - Fix server list error when format is json.

Signed-off-by: Vivek Singh <ffdfd29e24c206a3c24e1247563eb4c218c7ffa5@msystechnologies.com>

MsysTechnologiesllc/knife-ec2,MsysTechnologiesllc/knife-ec2,ClogenyTechnologies/knife-ec2,chef/knife-ec2,chef/knife-ec2