COMP: fix find_boost and find_boost unit_test_framework

Modules/ThirdParty/Boost/otb-module-init.cmake

-# Optional components
-if (BUILD_TESTING)
-  set(OTB_Boost_COMPONENTS unit_test_framework)
-endif()
+find_package (Boost 1.35.0 REQUIRED)
 
-message(STATUS "Looking for boost components: ${OTB_Boost_COMPONENTS}")
-find_package ( Boost
-  1.35.0
-  COMPONENTS ${OTB_Boost_COMPONENTS}
-  REQUIRED
-  )
+if (BUILD_TESTING)
+  find_package (Boost 1.35.0 QUIET
+    COMPONENTS unit_test_framework)
+  if (NOT Boost_UNIT_TEST_FRAMEWORK_FOUND)
+    message(STATUS "Boost unit_test_framework not found. Hence otbOGRTests will be skipped")
+  else()
+    message(STATUS "Found Boost components: ${OTB_Boost_COMPONENTS}")
+  endif()
+endif() #BUILD_TESTING