psutils: Move functions from updater to utils

Move common, utility functions from updater.*pp to utils.*pp.  This will
enable those functions to be used by other command line options in the
psutils tool.

Modify --get-version and --get-model to use the new utility functions.

Also update --get-version to provide a single getVersion() function that
handles the existence of the psu.json file as a low-level implementation
detail.

Tested:
* Verified all automated tests run successfully
* Verified --get-version still works
  * With psu.json file
  * Without psu.json file
* Verified --get-model still works
  * With psu.json file
  * Without psu.json file
* Verified --update still gets correct device path, device name, and I2C
  bus/address from functions that moved to utils.*pp
* The complete test plan is available at
  https://gist.github.com/smccarney/c049e24655d32e22cab9d521d145774a

Change-Id: I51ceca10957dc9a924d0d7516dc29632a6ed82d3
Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
diff --git a/tools/power-utils/main.cpp b/tools/power-utils/main.cpp
index 8ca7c04..236f0d6 100644
--- a/tools/power-utils/main.cpp
+++ b/tools/power-utils/main.cpp
@@ -13,11 +13,8 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
-#include "config.h"
-
 #include "model.hpp"
 #include "updater.hpp"
-#include "utils.hpp"
 #include "version.hpp"
 
 #include <CLI/CLI.hpp>
@@ -55,18 +52,10 @@
 
     std::string ret;
 
-    bool useJsonFile = utils::checkFileExists(PSU_JSON_PATH);
     auto bus = sdbusplus::bus::new_default();
     if (!psuPathVersion.empty())
     {
-        if (!useJsonFile)
-        {
-            ret = version::getVersion(bus, psuPathVersion);
-        }
-        else
-        {
-            ret = version::getVersion(psuPathVersion);
-        }
+        ret = version::getVersion(bus, psuPathVersion);
     }
     if (!psuPathModel.empty())
     {