qdev-monitor: Fix crash when device_add is called with abstract driver

qdev-monitor: Fix crash when device_add is called with abstract driver

User is able to crash running QEMU when following monitor
command is called:

 device_add intel-hda-generic

Crash is caused by assertion in object_initialize_with_type()
when type is abstract.

Checking if type is abstract before instance is created in
qdev_device_add() allows to prevent crash on incorrect user input.

Cc: qemu-stable@nongnu.org
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Signed-off-by: Andreas Färber <afaerber@suse.de>
(cherry picked from commit 2fa4e56d88aa0039062bbc7f9a88e9f90c77ed94)

Conflicts:

	qdev-monitor.c

*updated to reflect different 1.6 variable names

Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>