Guests with large memory requirements can use default flavors, so
removing the special flavor for ppc64 since new qemu requires more
memory - http://wiki.qemu.org/ChangeLog/2.4 - PowerPC.
Users should set DEFAULT_INSTANCE_TYPE to one of the default
flavors available in local.conf, as m1.tiny.
DocImpact
Change-Id: I0fd275dc7342cc2daa83e9a2bd79d30e7defa3e4