maint: fix missing spaces in message

maint: fix missing spaces in message

I got an off-list report about a bad diagnostic:
Target network card mac 52:54:00:49:07:ccdoes not match source 52:54:00:49:07:b8

True to form, I've added a syntax check rule to prevent it
from recurring, and found several other offenders.

* cfg.mk (sc_require_whitespace_in_translation): New rule.
* src/conf/domain_conf.c (virDomainNetDefCheckABIStability): Add
space.
* src/esx/esx_util.c (esxUtil_ParseUri): Likewise.
* src/qemu/qemu_command.c (qemuCollectPCIAddress): Likewise.
* src/qemu/qemu_driver.c (qemuDomainSetMetadata)
(qemuDomainGetMetadata): Likewise.
* src/qemu/qemu_hotplug.c (qemuDomainChangeNetBridge): Likewise.
* src/rpc/virnettlscontext.c
(virNetTLSContextCheckCertDNWhitelist): Likewise.
* src/vmware/vmware_driver.c (vmwareDomainResume): Likewise.
* src/vbox/vbox_tmpl.c (vboxDomainGetXMLDesc, vboxAttachDrives):
Avoid false negatives.
* tools/virsh-domain.c (info_save_image_dumpxml): Reword.
Based on a report by Luwen Su.