Upgrade to mongo-java-driver 2.12.3

Closes #1401

Author: wilkinsona

spring-boot-dependencies/pom.xml

@@ -89,7 +89,7 @@
 		<log4j.version>1.2.17</log4j.version>
 		<logback.version>1.1.2</logback.version>
 		<mockito.version>1.9.5</mockito.version>
-		<mongodb.version>2.12.2</mongodb.version>
+		<mongodb.version>2.12.3</mongodb.version>
 		<mysql.version>5.1.31</mysql.version>
 		<reactor.version>1.1.2.RELEASE</reactor.version>
 		<servlet-api.version>3.0.1</servlet-api.version>