Exclude httpclient from fcrepo-integration-ldp project.

To show what the dependency tree looks like without the exclusion of httpclient, I temporarily removed that exclusion from fcrepo-integration-ldp/pom.xml, and ran:
`mvn dependency:tree -pl fcrepo-integration-ldp/`

Here is the pertinent snippet:
> [INFO] +- org.openrdf.sesame:sesame-sail-memory:jar:2.7.13:test
> [INFO] |  +- org.openrdf.sesame:sesame-sail-inferencer:jar:2.7.13:test
> [INFO] |  |  +- org.openrdf.sesame:sesame-queryparser-api:jar:2.7.13:test
> [INFO] |  |  \- org.openrdf.sesame:sesame-queryparser-serql:jar:2.7.13:test
> [INFO] |  \- org.openrdf.sesame:sesame-queryalgebra-evaluation:jar:2.7.13:test
> [INFO] |     +- org.openrdf.sesame:sesame-repository-sparql:jar:2.7.13:test
> [INFO] |     |  +- org.openrdf.sesame:sesame-queryparser-sparql:jar:2.7.13:test
> [INFO] |     |  \- org.openrdf.sesame:sesame-queryresultio-sparqlxml:jar:2.7.13:test
> [INFO] |     \- org.openrdf.sesame:sesame-http-client:jar:2.7.13:test
> [INFO] |        +- org.openrdf.sesame:sesame-http-protocol:jar:2.7.13:test
> [INFO] |        \- commons-httpclient:commons-httpclient:jar:3.1:test