This patch changes the top level handlers to coroutines and sets the base.
It will be followed up with series of patches to convert all filesystem
calls to threaded coroutines pushing all blocking clals in VirtFS out
of vcpu threads.

Signed-off-by: Venkateswararao Jujjuri "<jvrao@linux.vnet.ibm.com>
Signed-off-by: NAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>