build: remove some dead assignments

No syntactic effect; this merely silences some clang warnings.

* src/libxl/libxl_driver.c (libxlDomainSetVcpusFlags): Drop
redundant ret=0 statement.
* src/qemu/qemu_monitor_text.c (qemuMonitorTextDriveDel):
Likewise.

src/libxl/libxl_driver.c

@@ -1703,7 +1703,6 @@ libxlDomainSetVcpusFlags(virDomainPtr dom, unsigned int nvcpus,
         def->maxvcpus = nvcpus;
         if (nvcpus < def->vcpus)
             def->vcpus = nvcpus;
-        ret = 0;
         break;
 
     case VIR_DOMAIN_VCPU_CONFIG:

src/qemu/qemu_monitor_text.c

@@ -2396,7 +2396,6 @@ int qemuMonitorTextDriveDel(qemuMonitorPtr mon,
     } else if (STRPREFIX(reply, "Device '") && (strstr(reply, "not found"))) {
         /* NB: device not found errors mean the drive was auto-deleted and we
          * ignore the error */
-        ret = 0;
     } else if (STRNEQ(reply, "")) {
         qemuReportError(VIR_ERR_OPERATION_FAILED,
                         _("deleting %s drive failed: %s"), drivestr, reply);