engine: [cleanup] Rename Initialize to initialize

Findbugs warning message:
Backend.java:171, NM_METHOD_NAMING_CONVENTION, Priority: Low

The method name org.ovirt.engine.core.bll.Backend.Initialize() doesn't start
with a lower case letter

Methods should be verbs, in mixed case with the first letter lowercase, with
the first letter of each internal word capitalized.

Change-Id: I2b48a9368fedd5da6eea764b773785e6df16db23
Signed-off-by: Adam Litke <alitke@redhat.com>