qemu_driver.c: validate 'driverName' earlier in qemuNodeDeviceDetachFlags()
qemu_driver.c: validate 'driverName' earlier in qemuNodeDeviceDetachFlags()

The validation of 'driverName' does not depend on any other state and can be
done right on the start of the function. We can fail earlier while avoiding
a cleanup jump.

Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Signed-off-by: Daniel Henrique Barboza <627b089ad62deae9aaf06ccfa2c9056df28927e0@gmail.com>

jfehlig/libvirt,olafhering/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,olafhering/libvirt,olafhering/libvirt,nertpinx/libvirt,nertpinx/libvirt,libvirt/libvirt,crobinso/libvirt,jfehlig/libvirt,libvirt/libvirt,libvirt/libvirt,nertpinx/libvirt,zippy2/libvirt,nertpinx/libvirt,jfehlig/libvirt,libvirt/libvirt,crobinso/libvirt,olafhering/libvirt,crobinso/libvirt,crobinso/libvirt,zippy2/libvirt,zippy2/libvirt