Fix Ruby warnings

MSP-12656

spec_helper enables Ruby warnings now, so fix those under this project's
control.

spec/app/models/metasploit/model/search/query_spec.rb

@@ -612,8 +612,8 @@
 
         it 'should have same operator for each child of a union' do
           children.each do |child|
-            operator_set = child.children.inject(Set.new) { |operator_set, operation|
-              operator_set.add operation.operator
+            operator_set = child.children.inject(Set.new) { |block_operator_set, operation|
+              block_operator_set.add operation.operator
             }
 
             expect(operator_set.length).to eq(1)

spec/lib/metasploit/model/nilify_blanks_spec.rb

@@ -37,7 +37,7 @@
     it 'should support adding multiple attributes' do
       attributes = [:a, :b]
 
-      base_class.nilify_blank *attributes
+      base_class.nilify_blank(*attributes)
 
       attributes.each do |attribute|
         expect(base_class.nilify_blank_attribute_set).to include(attribute)

spec/lib/metasploit/model/search/association_spec.rb

@@ -54,7 +54,7 @@
 
   context 'search_associations' do
     subject(:search_associations) {
-      base_class.search_associations *associations
+      base_class.search_associations(*associations)
     }
 
     let(:associations) {

spec/lib/metasploit/model/spec/i18n_exception_handler_spec.rb

@@ -30,7 +30,7 @@
       expect {
         call
       }.to raise_error(converted_exception.class) do |actual_exception|
-        actual_exception.class == converted_exception.class
+        expect(actual_exception.class).to eq(converted_exception.class)
         expect(actual_exception.key).to eq(converted_exception.key)
         expect(actual_exception.locale).to eq(converted_exception.locale)
         expect(actual_exception.options).to eq(converted_exception.options)

spec/lib/metasploit/model/spec_spec.rb

@@ -105,7 +105,11 @@
       expect {
         described_class.temporary_pathname = temporary_pathname
       }.to change {
-        described_class.instance_variable_get(:@temporary_pathname)
+                   if described_class.instance_variable_defined? :@temporary_pathname
+                     described_class.instance_variable_get(:@temporary_pathname)
+                   else
+                     nil
+                   end
       }.to(temporary_pathname)
     end
   end