vhci: Check whether vhci open setup succeeded

Due to race condition in the vhci kernel driver, we might read not a
vendor response packet, but a HCI reset command. This extra check will
ensure that kernel driver behaves correctly. Otherwise, the HCI setup
process will fail, because our controller will not respond to "missing"
HCI reset command. In result the virtual HCI will be DOWN and without
initialized Bluetooth address, e.g:

> hciconfig
hci2:   Type: Primary  Bus: Virtual
        BD Address: 00:AA:01:01:00:02  ACL MTU: 192:1  SCO MTU: 0:0
        UP RUNNING
        RX bytes:0 acl:0 sco:0 events:66 errors:0
        TX bytes:3086 acl:0 sco:0 commands:66 errors:0

hci1:   Type: Primary  Bus: Virtual
        BD Address: 00:00:00:00:00:00  ACL MTU: 0:0  SCO MTU: 0:0
        DOWN
        RX bytes:0 acl:0 sco:0 events:0 errors:0
        TX bytes:8 acl:0 sco:0 commands:1 errors:0

> dmesg
[1754256.640122] Bluetooth: MGMT ver 1.22
[1754263.023806] Bluetooth: MGMT ver 1.22
[1754265.043775] Bluetooth: hci1: Opcode 0x c03 failed: -110

emulator/vhci.c

@@ -122,14 +122,16 @@ struct vhci *vhci_open(uint8_t type)
 		break;
 	}
 
-	if (write(fd, &req, sizeof(req)) < 0) {
+	if (write(fd, &req, sizeof(req)) != sizeof(req)) {
 		close(fd);
 		return NULL;
 	}
 
 	memset(&rsp, 0, sizeof(rsp));
 
-	if (read(fd, &rsp, sizeof(rsp)) < 0) {
+	if (read(fd, &rsp, sizeof(rsp)) != sizeof(rsp) ||
+			rsp.pkt_type != HCI_VENDOR_PKT ||
+			rsp.opcode != req.opcode) {
 		close(fd);
 		return NULL;
 	}