maint: use consistent if-else braces in qemu
    
    I'm about to add a syntax check that enforces our documented
    HACKING style of always using matching {} on if-else statements.
    
    This commit focuses on the qemu driver.
    
    * src/qemu/qemu_command.c (qemuParseISCSIString)
    (qemuParseCommandLineDisk, qemuParseCommandLine)
    (qemuBuildSmpArgStr, qemuBuildCommandLine)
    (qemuParseCommandLineDisk, qemuParseCommandLineSmp): Correct use
    of {}.
    * src/qemu/qemu_capabilities.c (virQEMUCapsProbeCPUModels):
    Likewise.
    * src/qemu/qemu_driver.c (qemuDomainCoreDumpWithFormat)
    (qemuDomainRestoreFlags, qemuDomainGetInfo)
    (qemuDomainMergeBlkioDevice): Likewise.
    * src/qemu/qemu_hotplug.c (qemuDomainAttachNetDevice): Likewise.
    * src/qemu/qemu_monitor_text.c (qemuMonitorTextCreateSnapshot)
    (qemuMonitorTextLoadSnapshot, qemuMonitorTextDeleteSnapshot):
    Likewise.
    * src/qemu/qemu_process.c (qemuProcessStop): Likewise.
    
    Signed-off-by: Eric Blake <eblake@redhat.com>