DATACOUCH-235 - Fixed multiple Couchbase environments.

Defining <couchbase:env/> in XML configuration was causing a double
instantiation of DefaultCoreEnvironment, with subsequent warning in
logs:

[main] WARN c.c.client.core.env.CoreEnvironment - More than 1 Couchbase
Environments found (2), this can have severe impact on performance and
stability. Reuse environments!

src/test/resources/configurations/couchbaseSingleEnv-bean.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<beans xmlns="http://www.springframework.org/schema/beans"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xmlns:couchbase="http://www.springframework.org/schema/data/couchbase"
+       xsi:schemaLocation="http://www.springframework.org/schema/data/couchbase http://www.springframework.org/schema/data/couchbase/spring-couchbase.xsd
+                           http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
+                           http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">
+
+    <couchbase:env id="singleEnv"/>
+
+</beans>