regulators: Enhance config file parser

Enhance JSON config file parser to convert relative inventory paths to
absolute form.

Tested:
Run local CI with -Dlong-tests=enabled to enable tests for
validate-regulators-config.py.

Signed-off-by: Bob King <Bob_King@wistron.com>
Change-Id: I80237a673f9c5918898db15363847722141388e6
diff --git a/phosphor-regulators/test/system_tests.cpp b/phosphor-regulators/test/system_tests.cpp
index 809d2d4..d5b5b1a 100644
--- a/phosphor-regulators/test/system_tests.cpp
+++ b/phosphor-regulators/test/system_tests.cpp
@@ -242,7 +242,8 @@
     std::unique_ptr<PresenceDetection> presenceDetection{};
     std::unique_ptr<Configuration> deviceConfiguration{};
     std::unique_ptr<Device> device = std::make_unique<Device>(
-        "reg1", true, "/system/chassis/motherboard/reg1",
+        "reg1", true,
+        "/xyz/openbmc_project/inventory/system/chassis/motherboard/reg1",
         std::move(i2cInterface), std::move(presenceDetection),
         std::move(deviceConfiguration), std::move(rails));