Fix problem on Jenkins cppcheck job

Fix grep command that counts cppcheck errors
In order to trigger the job on Jenkins for this PR I have also
modified a couple of C++ files - specifically I have resolved a
cppcheck warning on method parameter in one of my algorithms
(CalculateMultipleScattering)

Framework/Algorithms/inc/MantidAlgorithms/CalculateMultipleScattering.h

@@ -77,7 +77,7 @@ private:
                               Kernel::V3D sourcePos, Kernel::PseudoRandomNumberGenerator &rng);
   Geometry::Track generateInitialTrack(const Geometry::IObject &shape,
                                        std::shared_ptr<const Geometry::ReferenceFrame> frame,
-                                       const Kernel::V3D sourcePos, Kernel::PseudoRandomNumberGenerator &rng);
+                                       const Kernel::V3D &sourcePos, Kernel::PseudoRandomNumberGenerator &rng);
   void inc_xyz(Geometry::Track &track, double vl);
   void updateWeightAndPosition(Geometry::Track &track, double &weight, const double vmfp, const double sigma_total,
                                Kernel::PseudoRandomNumberGenerator &rng);

Framework/Algorithms/src/CalculateMultipleScattering.cpp

@@ -651,7 +651,7 @@ void CalculateMultipleScattering::updateWeightAndPosition(Geometry::Track &track
  */
 Geometry::Track CalculateMultipleScattering::generateInitialTrack(const Geometry::IObject &shape,
                                                                   std::shared_ptr<const Geometry::ReferenceFrame> frame,
-                                                                  const V3D sourcePos,
+                                                                  const V3D &sourcePos,
                                                                   Kernel::PseudoRandomNumberGenerator &rng) {
   auto sampleBox = shape.getBoundingBox();
   // generate random point on front surface of sample bounding box

buildconfig/Jenkins/cppcheck.sh

@@ -4,7 +4,7 @@ SCRIPT_DIR=$(dirname "$0")
 # If errors slip through to master this can be used to set a non-zero
 # allowed count while those errors are dealt with. This avoids breaking all
 # builds for all developers
-ALLOWED_ERRORS_COUNT=288
+ALLOWED_ERRORS_COUNT=287
 
 if [[ ${JOB_NAME} == *pull_requests* ]]; then
     # This relies on the fact pull requests use pull/$PR-NAME
@@ -41,7 +41,7 @@ cmake --build . --target cppcheck
 cppcheck-htmlreport --file=cppcheck.xml --title=Embedded --report-dir=cppcheck-report
 
 # Mark build as passed or failed
-errors_count=$(grep -c '</error>' $1)
+errors_count=$(grep -c '</error>' cppcheck.xml)
 if [ $errors_count -gt ${ALLOWED_ERRORS_COUNT} ]; then
   echo "CppCheck found ${ALLOWED_ERRORS_COUNT} errors."
   echo "See CppCheck link on the job page for more detail."