coverity: fixed issue argument cannot be negative

sesman/chansrv/devredir.c

@@ -118,7 +118,7 @@ dev_redir_init(void)
     } u;
 
     /* get a random number that will act as a unique clientID */
-    if ((fd = open("/dev/urandom", O_RDONLY)))
+    if ((fd = open("/dev/urandom", O_RDONLY)) != -1)
     {
         if (read(fd, u.buf, 4) != 4)
         {

sesman/tools/dis.c

@@ -58,7 +58,12 @@ int main(int argc, char **argv)
         return 1;
     }
 
-    sck = socket(PF_UNIX, SOCK_DGRAM, 0);
+    if ((sck = socket(PF_UNIX, SOCK_DGRAM, 0)) < 0)
+    {
+        printf("socket open error\n");
+        return 1;
+    }
+
     len = sizeof(sa);
 
     if (sendto(sck, "sig", 4, 0, (struct sockaddr *)&sa, len) > 0)

xrdpapi/xrdpapi.c

@@ -124,7 +124,11 @@ WTSVirtualChannelOpenEx(unsigned int SessionId, const char *pVirtualName,
     }
 
     /* we use unix domain socket to communicate with chansrv */
-    wts->fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if ((wts->fd = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
+    {
+        g_free(wts);
+        return NULL;
+    }
 
     /* set non blocking */
     llong = fcntl(wts->fd, F_GETFL);