Add trailing escape character test

Update `OriginTrackedPropertiesLoaderTests` to also test that an escape
character can be the last character on a line.

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/OriginTrackedPropertiesLoaderTests.java

 /*
- * Copyright 2012-2019 the original author or authors.
+ * Copyright 2012-2020 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -248,6 +248,12 @@ class OriginTrackedPropertiesLoaderTests {
 		assertThat(getValue(value)).isEqualTo("trailing ");
 	}
 
+	@Test
+	void getPropertyWithEscapedTrailingSpace() {
+		OriginTrackedValue value = this.properties.get("test-with-escaped-trailing-space");
+		assertThat(getValue(value)).isEqualTo("trailing ");
+	}
+
 	private Object getValue(OriginTrackedValue value) {
 		return (value != null) ? value.getValue() : null;
 	}

spring-boot-project/spring-boot/src/test/resources/org/springframework/boot/env/test-properties.properties

@@ -42,3 +42,4 @@ test-multiline-immediate-bang=\
 test-iso8859-1-chars=
 
 test-with-trailing-space= trailing 
+test-with-escaped-trailing-space= trailing\