mapFields: reset the FOAM_CASE environment variable

Patch proveded by Alexey Matveichev
Resolves bug-report http://bugs.openfoam.org/view.php?id=2229

applications/utilities/preProcessing/mapFields/createTimes.H

     Info<< "\nCreate databases as time" << endl;
 
+    const auto caseDirOrig = getEnv("FOAM_CASE");
+    const auto caseNameOrig = getEnv("FOAM_CASE_NAME");
+    setEnv("FOAM_CASE", rootDirSource/caseDirSource, true);
+    setEnv("FOAM_CASE_NAME", caseDirSource, true);
     Time runTimeSource
     (
         Time::controlDictName,
         rootDirSource,
         caseDirSource
     );
+    setEnv("FOAM_CASE", caseDirOrig, true);
+    setEnv("FOAM_CASE_NAME", caseNameOrig, true);
 
     Time runTimeTarget
     (

applications/utilities/preProcessing/mapFields/mapFields.C

@@ -236,8 +236,8 @@ int main(int argc, char *argv[])
     fileName rootDirTarget(args.rootPath());
     fileName caseDirTarget(args.globalCaseName());
 
-    const fileName casePath = args[1];
-    const fileName rootDirSource = casePath.path();
+    fileName casePath = args[1];
+    const fileName rootDirSource = casePath.path().toAbsolute();
     const fileName caseDirSource = casePath.name();
 
     Info<< "Source: " << rootDirSource << " " << caseDirSource << endl;