simplify convert_from_string calls

There were a few sdbusplus convert_from_string calls added with
commit 7b4d59aa8f6020b919d41415bece7f0651304b00.  Simplify these
to reduce the duplicate string-conversion calls and to improve
readability.

Change-Id: Iec688fb88dc2513d42583af110abd4c04aeb9fa0
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
diff --git a/host-bmc/dbus_to_host_effecters.cpp b/host-bmc/dbus_to_host_effecters.cpp
index b16c750..d83b4d9 100644
--- a/host-bmc/dbus_to_host_effecters.cpp
+++ b/host-bmc/dbus_to_host_effecters.cpp
@@ -164,19 +164,18 @@
     {
         auto propVal = dbusHandler->getDbusPropertyVariant(
             hostStatePath, "BootProgress", BootProgress::interface);
-        const auto& currHostState = std::get<std::string>(propVal);
-        if ((sdbusplus::message::convert_from_string<
-                 BootProgress::ProgressStages>(currHostState) !=
-             BootProgress::ProgressStages::SystemInitComplete) &&
-            (sdbusplus::message::convert_from_string<
-                 BootProgress::ProgressStages>(currHostState) !=
-             BootProgress::ProgressStages::OSRunning) &&
-            (sdbusplus::message::convert_from_string<
-                 BootProgress::ProgressStages>(currHostState) !=
-             BootProgress::ProgressStages::SystemSetup))
+
+        using Stages = BootProgress::ProgressStages;
+        auto currHostState = sdbusplus::message::convert_from_string<Stages>(
+                                 std::get<std::string>(propVal))
+                                 .value();
+
+        if (currHostState != Stages::SystemInitComplete &&
+            currHostState != Stages::OSRunning &&
+            currHostState != Stages::SystemSetup)
         {
             info("Host is not up. Current host state: {CUR_HOST_STATE}",
-                 "CUR_HOST_STATE", currHostState.c_str());
+                 "CUR_HOST_STATE", currHostState);
             return;
         }
     }