Remove whitespace from id file on load

If the id file includes whitespace, remove it. If the content of
the id file is empty, do not set the machine id.

Fixes: #10722

lib/vagrant/machine.rb

@@ -399,7 +399,10 @@ module Vagrant
         # Read the id file from the data directory if it exists as the
         # ID for the pre-existing physical representation of this machine.
         id_file = @data_dir.join("id")
-        @id = id_file.read.chomp if id_file.file?
+        id_content = id_file.read.strip if id_file.file?
+        if !id_content.to_s.empty?
+          @id = id_content
+        end
       end
 
       if @id != old_id && @provider

test/unit/vagrant/machine_test.rb

@@ -912,4 +912,62 @@ describe Vagrant::Machine do
       expect(subject.ui).to_not equal(ui)
     end
   end
+
+  describe "#reload" do
+    context "when ID is unset and id file does not exist" do
+      it "should remain nil" do
+        expect(subject.id).to be_nil
+        instance.reload
+        expect(subject.id).to be_nil
+      end
+    end
+
+    context "when id file is set" do
+      let(:id_content) { "test-machine-id" }
+
+      before do
+        id_file = subject.data_dir.join("id")
+        File.write(id_file.to_s, id_content)
+      end
+
+      it "should update the machine id" do
+        expect(subject.id).to be_nil
+        instance.reload
+        expect(subject.id).to eq(id_content)
+      end
+
+      it "should notify of the id change when provider is set" do
+        expect(provider).to receive(:machine_id_changed)
+        instance.reload
+      end
+
+      context "when id file content includes whitespace" do
+        let(:id_content) { "   test-machine-id\n" }
+
+        it "should remove all whitespace" do
+          instance.reload
+          expect(instance.id).to eq("test-machine-id")
+        end
+      end
+
+      context "when id file content is all whitespace" do
+        let(:id_content) { "\0\0\0\0\0\0" }
+
+        it "should not update the id" do
+          expect(instance.id).to be_nil
+          instance.reload
+          expect(instance.id).to be_nil
+        end
+      end
+
+      context "when id is already set to value in id file" do
+        it "should not notify of id change" do
+          instance.instance_variable_set(:@id, id_content)
+          expect(provider).not_to receive(:machine_id_changed)
+          instance.reload
+          expect(instance.id).to eq(id_content)
+        end
+      end
+    end
+  end
 end