[CID-1219446] - Resource leak in ClassicPluginStrategy

Resource leak may happen during the search of manifest file.
Signed-off-by: NOleg Nenashev <o.v.nenashev@gmail.com>

core/src/main/java/hudson/ClassicPluginStrategy.java

@@ -116,22 +116,32 @@ public class ClassicPluginStrategy implements PluginStrategy {
     }
 
     private static Manifest loadLinkedManifest(File archive) throws IOException {
-            // resolve the .hpl file to the location of the manifest file
-            final String firstLine = IOUtils.readFirstLine(new FileInputStream(archive), "UTF-8");
-            if (firstLine.startsWith("Manifest-Version:")) {
-                // this is the manifest already
-            } else {
-                // indirection
-                archive = resolve(archive, firstLine);
-            }
-            // then parse manifest
-            FileInputStream in = new FileInputStream(archive);
+            // resolve the .hpl file to the location of the manifest file        
             try {
-                return new Manifest(in);
+                // Locate the manifest
+                String firstLine;
+                FileInputStream manifestHeaderInput = new FileInputStream(archive);
+                try {
+                    firstLine = IOUtils.readFirstLine(manifestHeaderInput, "UTF-8");
+                } finally {
+                    manifestHeaderInput.close();
+                }
+                if (firstLine.startsWith("Manifest-Version:")) {
+                    // this is the manifest already
+                } else {
+                    // indirection
+                    archive = resolve(archive, firstLine);
+                }
+                
+                // Read the manifest
+                FileInputStream manifestInput = new FileInputStream(archive);
+                try {
+                    return new Manifest(manifestInput);
+                } finally {
+                    manifestInput.close();
+                }
             } catch (IOException e) {
                 throw new IOException("Failed to load " + archive, e);
-            } finally {
-                in.close();
             }
     }