Simplify select.map to filter_map

This commit simplifies instances where map is called on a select call to
instead use filter_map.

spec/unit/functions/lookup_fixture_spec.rb

@@ -47,7 +47,7 @@ def compile_and_get_notifications(code)
     Puppet[:code] = code
     node.environment.check_for_reparse
     catalog = block_given? ? compiler.compile { |cat| yield(compiler.topscope); cat } : compiler.compile
-    catalog.resources.map(&:ref).select { |r| r.start_with?('Notify[') }.map { |r| r[7..-2] }
+    catalog.resources.map(&:ref).filter_map { |r| r[7..-2] if r.start_with?('Notify[') }
   end
 
   # There is a fully configured 'production' environment in fixtures at this location
@@ -376,7 +376,7 @@ def compile_and_get_notifications(code)
         Puppet[:code] = "include bad_data\nlookup('bad_data::b')"
         expect { compiler.compile }.to raise_error(Puppet::ParseError, /did not find a value for the name 'bad_data::b'/)
       end
-      warnings = logs.select { |log| log.level == :warning }.map { |log| log.message }
+      warnings = logs.filter_map { |log| log.message if log.level == :warning }
       expect(warnings).to include("Module 'bad_data': Value returned from deprecated API function 'bad_data::data' must use keys qualified with the name of the module; got b")
     end
 
@@ -390,7 +390,7 @@ def compile_and_get_notifications(code)
         PUPPET
         expect(resources).to include('module_c')
       end
-      warnings = logs.select { |log| log.level == :warning }.map { |log| log.message }
+      warnings = logs.filter_map { |log| log.message if log.level == :warning }
       expect(warnings).to include("Module 'bad_data': Value returned from deprecated API function 'bad_data::data' must use keys qualified with the name of the module; got b")
     end