util: Remove '\n' from vhostuser ifname

When deleting the vhostuserclient interface, OVS prompts that the interface does not exist,
Through the XML file, I found that the "target dev" has a '\n', results in an XML parsing error.

XML file:

<target dev='vm-20ac9c030a47
'/>

That is because 'ovs-vsctl' returns a newline result, always come with a '\n',
and the vircommandrun function puts it in ifname.

So virNetDevOpenvswitchGetVhostuserIfname should remove '\n' from ifname.

Signed-off-by: Yalei Li <liyl43@chinatelecom.cn>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>

src/util/virnetdevopenvswitch.c

@@ -575,6 +575,7 @@ virNetDevOpenvswitchGetVhostuserIfname(const char *path,
         return 0;
     }
 
+    virStringTrimOptionalNewline(*ifname);
     if (virNetDevOpenvswitchMaybeUnescapeReply(*ifname) < 0) {
         VIR_FREE(*ifname);
         return -1;