Fix a non fatal exception during a testrun when injecting LDAPSecurityRealm.

org.apache.commons.io.input.AutoCloseInputStream was introduced in commons-io version 1.4. The stapler dependency made maven select the 1.3.1 version of commons-io.
Merge pull request #47 from spark404/fix-compileerror

Fix a non fatal exception during a testrun when injecting LDAPSecurityRealm