hypervisor: utilize const for currentHostState()

As noted in the referenced bug, need to add a const for the override of
host state in the hypervisor class to match up with the base class from
phosphor-dbus-interfaces.

Fixes openbmc/phosphor-state-manager#24

Tested:
- Verified it compiled

Change-Id: Ic8469dbe0a06b9b0c7ce8efb1867fcde9f3b0b6d
Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
diff --git a/hypervisor_state_manager.cpp b/hypervisor_state_manager.cpp
index da4d37f..dbad524 100644
--- a/hypervisor_state_manager.cpp
+++ b/hypervisor_state_manager.cpp
@@ -54,7 +54,7 @@
     return server::Host::currentHostState(value);
 }
 
-server::Host::HostState Hypervisor::currentHostState()
+server::Host::HostState Hypervisor::currentHostState() const
 {
     return server::Host::currentHostState();
 }
diff --git a/hypervisor_state_manager.hpp b/hypervisor_state_manager.hpp
index 6253c38..b1552d3 100644
--- a/hypervisor_state_manager.hpp
+++ b/hypervisor_state_manager.hpp
@@ -62,7 +62,7 @@
         currentHostState(server::Host::HostState value) override;
 
     /** @brief Return value of CurrentHostState */
-    server::Host::HostState currentHostState();
+    server::Host::HostState currentHostState() const override;
 
     /** @brief Check if BootProgress change affects hypervisor state
      *