qemu: Double mutex unlock in qemuDomainModifyDeviceFlags

The driver mutex was unlocked in qemuDomainModifyDeviceFlags before
entering qemuDomainObjBeginJobWithDriver where it will be unlocked once
more leaving it in an undefined state. The result was that two
threads were simultaneously looking up the domain hash table during
multiple parallel device attach/detach operations.
Luckily this triggered a virHashIterationError.
Signed-off-by: NViktor Mihajlovski <mihajlov@linux.vnet.ibm.com>

src/qemu/qemu_driver.c

@@ -6443,7 +6443,6 @@ qemuDomainModifyDeviceFlags(virDomainPtr dom, const char *xml,
 
     qemuDriverLock(driver);
     vm = virDomainFindByUUID(&driver->domains, dom->uuid);
-    qemuDriverUnlock(driver);
     if (!vm) {
         char uuidstr[VIR_UUID_STRING_BUFLEN];
         virUUIDFormat(dom->uuid, uuidstr);