core: Move cpu_over_commit from VdsDynamic to VdsStatistics

cpu_over_commit field is rapidly changing, and should be located in VdsStatistics.
This patch moves it to vds_statistics and updates the relevant stored procedures
and DAOs

Change-Id: I604132f9f05c8470ff09196db77eea2957899e2a
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=1114285
Signed-off-by: lzelkha@redhat.com <lzelkha@redhat.com>