Fix AppServer build errors in Eclipse with <4.6 target platforms

Fix AppServer build errors in Eclipse with <4.6 target platforms

9aa3748 added dummy implementations for loadRoleInfo() and
loadUserInfo() to class MappedLoginService to fix compile errors in
Eclipse when using 4.6 target platform which brings Jetty 9.3 adding
these two methods. Unfortunately this causes errors when using non 4.6
target platform coming with an older Jetty version. Fix this by
extracting the anonymous subclass of MappedLoginService which allows to
suppress the unused private method errors in Eclipse.

Change-Id: I75baeea7ff4502ce9ef2b541b3c0555da5535d79
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>