engine: [cleanup] Rename RunPublicQuery to runPublicQuery

Findbugs warning message:
Backend.java:598, NM_METHOD_NAMING_CONVENTION, Priority: Low

The method name
org.ovirt.engine.core.bll.Backend.RunPublicQuery(VdcQueryType,
                                                 VdcQueryParametersBase)
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: If105d68de5ad76d61a9123efac5c14440a8a3032
Signed-off-by: Adam Litke <alitke@redhat.com>