psu-ng: Move test getUtils and freeUtils to cpp

While debugging an SDK build issue regarding optimization and
_FORTIFY_SORUCE, it was discovered that the tests for
phosphor-power-supply fail to link if meson is run with --buildtype
debugoptimized.

Tested:
     Builds with --buildtype debug
     Builds with --buildtype debugoptimized
     Builds with --buildtype plain

Signed-off-by: Brandon Wyman <bjwyman@gmail.com>
Change-Id: I095ecd83c85d5ed488f83cb3ede79c20701969a2
diff --git a/phosphor-power-supply/test/mock.cpp b/phosphor-power-supply/test/mock.cpp
index e13db2b..a68628b 100644
--- a/phosphor-power-supply/test/mock.cpp
+++ b/phosphor-power-supply/test/mock.cpp
@@ -1,4 +1,4 @@
-#include <mock.hpp>
+#include "mock.hpp"
 
 namespace phosphor
 {
@@ -10,6 +10,28 @@
 {
     return std::make_unique<MockedPMBus>();
 }
-
 } // namespace pmbus
+
+namespace power
+{
+namespace psu
+{
+static std::unique_ptr<MockedUtil> util;
+
+const UtilBase& getUtils()
+{
+    if (!util)
+    {
+        util = std::make_unique<MockedUtil>();
+    }
+    return *util;
+}
+
+void freeUtils()
+{
+    util.reset();
+}
+
+} // namespace psu
+} // namespace power
 } // namespace phosphor