Create linker namespace in startServiceFromJar

Previously the classloader would have no initialized linker namespace,
so JNI libraries associated with a JAR in an APEX would not be found.

Use ClassLoaderFactory to ensure that the linker namespace is
initialized.

Bug: 172541385
Test: manual: boot device with system server JAR using JNI in APEX
Change-Id: Icc94c70b3e3817aa637c32f1190faa41364e1604