release connections after each request

In running the jms-to-rest example, I hit the following error:
```
$ mvn exec:java -Dexec.mainClass="RestReceive" -e
[INFO] Error stacktraces are turned on.
[INFO] Scanning for projects...

<snip>

[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.1:java (default-cli) on project mixed-jms-rest: An exception occured while executing the Java class. null: InvocationTargetException: Invalid use of SingleClientConnManager: connection still allocated.
[ERROR] Make sure to release the connection before allocating another one.
[ERROR] -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.1:java (default-cli) on project mixed-jms-rest: An exception occured while executing the Java class. null
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:216)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:84)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:318)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:153)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:555)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:214)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:158)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
	at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
	at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:414)
	at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:357)
Caused by: org.apache.maven.plugin.MojoExecutionException: An exception occured while executing the Java class. null
	at org.codehaus.mojo.exec.ExecJavaMojo.execute(ExecJavaMojo.java:345)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:106)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
	... 19 more
Caused by: java.lang.reflect.InvocationTargetException
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:606)
	at org.codehaus.mojo.exec.ExecJavaMojo$1.run(ExecJavaMojo.java:290)
	at java.lang.Thread.run(Thread.java:724)
Caused by: java.lang.IllegalStateException: Invalid use of SingleClientConnManager: connection still allocated.
Make sure to release the connection before allocating another one.
	at org.apache.http.impl.conn.SingleClientConnManager.getConnection(SingleClientConnManager.java:216)
	at org.apache.http.impl.conn.SingleClientConnManager$1.getConnection(SingleClientConnManager.java:190)
	at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:401)
	at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:820)
	at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:754)
	at org.jboss.resteasy.client.core.executors.ApacheHttpClient4Executor.execute(ApacheHttpClient4Executor.java:109)
	at org.jboss.resteasy.core.interception.ClientExecutionContextImpl.proceed(ClientExecutionContextImpl.java:39)
	at org.jboss.resteasy.plugins.interceptors.encoding.AcceptEncodingGZIPInterceptor.execute(AcceptEncodingGZIPInterceptor.java:40)
	at org.jboss.resteasy.core.interception.ClientExecutionContextImpl.proceed(ClientExecutionContextImpl.java:45)
	at org.jboss.resteasy.client.ClientRequest.execute(ClientRequest.java:443)
	at org.jboss.resteasy.client.ClientRequest.httpMethod(ClientRequest.java:677)
	at org.jboss.resteasy.client.ClientRequest.post(ClientRequest.java:566)
	at RestReceive.main(RestReceive.java:22)
	... 6 more
```

Adding appropriate calls to `ClientResponse.releaseConnection()` solved the problem.