API: prevent query of --live and --config at once

API: prevent query of --live and --config at once

Drivers were inconsistent when presented both --live and --config
at once.  For example, within qemu, getting memory parameters
favored live, getting blkio tuning favored config, and getting
scheduler parameters errored out.  Also, some, but not all,
attempts to mix flags on query were filtered at the virsh level.
We shouldn't have to duplicate efforts in every client app, nor
in every driver.  So, it is simpler to just enforce that the two
flags cannot both be used at once on query operations, which has
precedent in libvirt.c, and which matches the documentation of
virDomainModificationImpact.

* src/libvirt.c (virDomainGetMemoryParameters)
(virDomainGetBlkioParameters)
(virDomainGetSchedulerParametersFlags, virDomainGetVcpuPinInfo):
Borrow sanity checking from virDomainGetVcpusFlags.