Description of problem:
Currently the "guest-info" virtagent command will returns all commands that are supported or unsupported.  And all of the are under the "supported_commands" list. 
We know that some of them are not supported in 6.3 but this may confuse customers.  As when sending a command like {"execute":"guest-file-open", "arguments":{"path":"/tmp/testqga","mode":"w+"}}. it will returns "unsupported command" though they are in the supported list.

It looks trival but it's fine to fix it.  For example, mark the "enabled" to false instead of true, etc.

 {"execute":"guest-info"}
{"return": {"version": "1.0", "supported_commands": [{"enabled": true, "name": "guest-suspend-hybrid"}, {"enabled": true, "name": "guest-suspend-ram"}, {"enabled": true, "name": "guest-suspend-disk"}, {"enabled": true, "name": "guest-fsfreeze-thaw"}, {"enabled": true, "name": "guest-fsfreeze-freeze"}, {"enabled": true, "name": "guest-fsfreeze-status"}, {"enabled": true, "name": "guest-file-flush"}, {"enabled": true, "name": "guest-file-seek"}, {"enabled": true, "name": "guest-file-write"}, {"enabled": true, "name": "guest-file-read"}, {"enabled": true, "name": "guest-file-close"}, {"enabled": true, "name": "guest-file-open"}, {"enabled": true, "name": "guest-shutdown"}, {"enabled": true, "name": "guest-info"}, {"enabled": true, "name": "guest-ping"}, {"enabled": true, "name": "guest-sync"}]}}


Version-Release number of selected component (if applicable):
qemu-kvm-0.12.1.2-2.265.el6.x86_64
qemu-guest-agent-0.12.1.2-2.265.el6.x86_64

How reproducible:
Always

Steps to Reproduce:
1.Boot a guest with virtio serial or isa serial attached. 
 /usr/libexec/qemu-kvm -M rhel6.3.0 -cpu Conroe -enable-kvm -m 2G -smp 2,sockets=1,cores=2,threads=1 -name rhel6.3 -uuid 26427d77-37e8-4217-ad98-140b16fa18f4 -device virtio-serial-pci,id=virtio-serial0,max_ports=16,bus=pci.0,addr=0x4 -drive file=/dev/vg-qzhang/lv-rhel6.3,if=none,id=drive-virtio-disk0,format=qcow2,cache=none,werror=stop,rerror=stop,aio=native -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0 -netdev tap,id=hostnet0,vhost=on,script=/etc/qemu-ifup -device virtio-net-pci,netdev=hostnet0,id=net0,mac=00:1a:2a:15:10:19,bus=pci.0 -drive file=/home/boot.iso,if=none,media=cdrom,id=drive-ide0-1-0,readonly=on,format=raw -device ide-drive,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0 -chardev socket,path=/tmp/qga.sock,server,nowait,id=qga0 -device virtserialport,chardev=qga0,name=org.qemu.guest_agent.0,bus=virtio-serial0.0 -vnc :10 -usb -device usb-tablet,id=input0 -device virtio-balloon-pci,id=balloon0,addr=0x7 -monitor stdio -boot c -rtc-td-hack -rtc base=localtime -qmp tcp:0:4444,server,nowait


2. Install qemu-guest-agent-0.12.1.2-2.265.el6.x86_64 inside guest.

3.On host: # nc -U /tmp/qga.sock
  
4. Inside guest: 
#qemu-ga -m virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent.0

5. Send command on host from the socket of step 3

# nc -U /tmp/qga.sock

 {"execute":"guest-info"}

6. {"execute":"guest-file-open", "arguments":{"path":"/tmp/testqga","mode":"w+"}}
{"error": {"class": "Unsupported", "data": {}}}


Actual results:
After step 5: 

{"return": {"version": "1.0", "supported_commands": [{"enabled": true, "name": "guest-suspend-hybrid"}, {"enabled": true, "name": "guest-suspend-ram"}, {"enabled": true, "name": "guest-suspend-disk"}, {"enabled": true, "name": "guest-fsfreeze-thaw"}, {"enabled": true, "name": "guest-fsfreeze-freeze"}, {"enabled": true, "name": "guest-fsfreeze-status"}, {"enabled": true, "name": "guest-file-flush"}, {"enabled": true, "name": "guest-file-seek"}, {"enabled": true, "name": "guest-file-write"}, {"enabled": true, "name": "guest-file-read"}, {"enabled": true, "name": "guest-file-close"}, {"enabled": true, "name": "guest-file-open"}, {"enabled": true, "name": "guest-shutdown"}, {"enabled": true, "name": "guest-info"}, {"enabled": true, "name": "guest-ping"}, {"enabled": true, "name": "guest-sync"}]}}

After step 6: 

{"error": {"class": "Unsupported", "data": {}}}

Expected results:
Mark the unsupported commands to make user know that are not supported yet.


Additional info: