Add hotplug design doc

This is a design document detailing the implementation of device
hotplugging in Ganeti.
Signed-off-by: Dimitris Aragiorgis <dimara@grnet.gr>
Reviewed-by: Guido Trotter <ultrotter@google.com>

Makefile.am

@@ -441,6 +441,7 @@ docinput = \
 	doc/design-cpu-pinning.rst \
 	doc/design-device-uuid-name.rst \
 	doc/design-draft.rst \
+	doc/design-hotplug.rst \
 	doc/design-htools-2.3.rst \
 	doc/design-http-server.rst \
 	doc/design-impexp2.rst \

doc/design-draft.rst

@@ -22,6 +22,7 @@ Design document drafts
    design-openvswitch.rst
    design-hugepages-support.rst
    design-cmdlib-unittests.rst
+   design-hotplug.rst
 
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