At the beginning of introspection, ironic inspector sets boot device and
reboot node through ironic, currently it only stops when reboot the node
is failed. Actually the node is not guaranteed to reboot with pxe in either
case.
This patch eliminates the descripency, so that if anything goes wrong, it
will be exposed early.
Change-Id: I416e42137e59e04f7fd282aa309f2f89cf574209
Story: #2002977
Task: #22985
chenjiao