openpower-pels: clean up various compile warnings

Compile warnings observed when compiling parts of the
openpower-pels (or corresponding tests) under stricter
compiler warning flags of Meson.

Issues fixed:
    - many unused parameters
    - invalid case fall-through
    - excess semi-colons
    - incorrect 'const' on return-by-value type
    - removal of variable length array in test case
    - uncaught return from 'system' call in test case

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I8af69184042cf8661d1307a02ecf3afcab4724a1
diff --git a/test/openpower-pels/pel_manager_test.cpp b/test/openpower-pels/pel_manager_test.cpp
index a2cb5fd..4ddf81b 100644
--- a/test/openpower-pels/pel_manager_test.cpp
+++ b/test/openpower-pels/pel_manager_test.cpp
@@ -813,7 +813,11 @@
     // Delete them all at once
     auto logPath = getPELRepoPath() / "logs";
     std::string cmd = "rm " + logPath.string() + "/*";
-    system(cmd.c_str());
+
+    {
+        auto rc = system(cmd.c_str());
+        EXPECT_EQ(rc, 0);
+    }
 
     EXPECT_EQ(countPELsInRepo(), 0);