things-manager: Fix cppcheck errors

things-manager: Fix cppcheck errors

This patch fixes the errors reported by cppcheck tool for '(error) Mismatching
allocation and deallocation: newActionSet'.
Replaced free() calls with delete wherever the memory is allocated using new().

Change-Id: Icc22a8c7658c29afb8ed60b5cd9926e69ce3e6fb
Signed-off-by: Ravi Nanjundappa <nravi.n@samsung.com>
Reviewed-on: https://gerrit.iotivity.org/gerrit/1506
Tested-by: jenkins-iotivity <jenkins-iotivity@opendaylight.org>
Reviewed-by: Erich Keane <erich.keane@intel.com>
Reviewed-by: Jihun Ha <jihun.ha@samsung.com>
Reviewed-by: Uze Choi <uzchoi@samsung.com>