Remove deprecated _ERROR_DATA_KEY in QMP
Remove deprecated _ERROR_DATA_KEY in QMP

Commit de253f14 of QEMU repo "BREAKS QMP's compatibility for
the error response" as it removes "data" key from qmp error
response messages.  To this end we only log "class" and "desc"
values of the message.

Signed-off-by: Dimitris Aragiorgis <4514117c4a99256e19437c7e3407c4ecbf98aec0@grnet.gr>
Signed-off-by: Stratos Psomadakis <1279c6adbafb38f35d4044d4e70c779d98ac212f@grnet.gr>
Reviewed-by: Jose A. Lopes <0fb9c4f8511df4ec2ae28af879e9d462f6218a2c@google.com>

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