PerformScan: Eliminate foundMatches

Erase elements from matches and test that it's not empty instead of
compiling a new foundMatches list only to compare their sizes.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I4d88ff872accef03d3b08670f388d2a94c44524e
diff --git a/src/PerformScan.cpp b/src/PerformScan.cpp
index ec2ad40..80f56b8 100644
--- a/src/PerformScan.cpp
+++ b/src/PerformScan.cpp
@@ -539,7 +539,6 @@
                                 continue;
                             }
 
-                            std::set<std::string> foundMatches;
                             for (auto& [configId, config] :
                                  _systemConfiguration.items())
                             {
@@ -569,7 +568,7 @@
                                         continue;
                                     }
 
-                                    foundMatches.insert(**match);
+                                    matches.erase(*match);
 
                                     if (isBind)
                                     {
@@ -585,7 +584,7 @@
                                     }
                                 }
                             }
-                            if (foundMatches.size() != matches.size())
+                            if (!matches.empty())
                             {
                                 std::cerr << "configuration file "
                                              "dependency error, "