QMP: test supported_commands
QMP: test supported_commands

Add test for supported_commands.

Signed-off-by: Apollon Oikonomopoulos <ed81ed0a45ccd5c8869bda52e38353a6299ee39e@gmail.com>
Signed-off-by: Thomas Thrainer <98bdeac947eb8ca18146e9ce7f092788ec242cd1@google.com>
Reviewed-by: Thomas Thrainer <98bdeac947eb8ca18146e9ce7f092788ec242cd1@google.com>

mbakke/ganeti,bitemyapp/ganeti,dimara/ganeti,leshchevds/ganeti,mbakke/ganeti,apyrgio/ganeti,grnet/snf-ganeti,ganeti/ganeti,yiannist/ganeti,dimara/ganeti,apyrgio/ganeti,ganeti-github-testing/ganeti-test-1,andir/ganeti,ganeti/ganeti,bitemyapp/ganeti,andir/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,onponomarev/ganeti,yiannist/ganeti,grnet/snf-ganeti,ganeti/ganeti,leshchevds/ganeti,leshchevds/ganeti,onponomarev/ganeti,mbakke/ganeti,andir/ganeti