regulators: Add configure support to Chassis class

Implemented the configure() method in the Chassis class.  This method
configures all the regulator devices within the chassis.

Also made very minor fixes to two testcases.

Signed-off-by: Shawn McCarney <shawnmm@us.ibm.com>
Change-Id: Ib29fdfa36e59f6b79d9467cdc52c3c6fc9c6886d
diff --git a/phosphor-regulators/test/validate-regulators-config_tests.cpp b/phosphor-regulators/test/validate-regulators-config_tests.cpp
index 987a492..139b3ca 100644
--- a/phosphor-regulators/test/validate-regulators-config_tests.cpp
+++ b/phosphor-regulators/test/validate-regulators-config_tests.cpp
@@ -221,7 +221,7 @@
 
 void expectCommandLineSyntax(const std::string& expectedErrorMessage,
                              const std::string& expectedOutputMessage,
-                             std::string command, int status)
+                             const std::string& command, int status)
 {
     std::string errorMessage;
     std::string outputMessage;