error: Replace qemu_error() by error_report()

error_report() terminates the message with a newline.  Strip it it
from its arguments.

This fixes a few error messages lacking a newline:
net_handle_fd_param()'s "No file descriptor named %s found", and
tap_open()'s "vnet_hdr=1 requested, but no kernel support for
IFF_VNET_HDR available" (all three versions).

There's one place that passes arguments without newlines
intentionally: load_vmstate().  Fix it up.
diff --git a/net/slirp.c b/net/slirp.c
index 7f846ec..b41c60a 100644
--- a/net/slirp.c
+++ b/net/slirp.c
@@ -413,14 +413,14 @@
 
     if (slirp_add_hostfwd(s->slirp, is_udp, host_addr, host_port, guest_addr,
                           guest_port) < 0) {
-        qemu_error("could not set up host forwarding rule '%s'\n",
-                   redir_str);
+        error_report("could not set up host forwarding rule '%s'",
+                     redir_str);
         return -1;
     }
     return 0;
 
  fail_syntax:
-    qemu_error("invalid host forwarding rule '%s'\n", redir_str);
+    error_report("invalid host forwarding rule '%s'", redir_str);
     return -1;
 }
 
@@ -473,10 +473,10 @@
         snprintf(cmd, sizeof(cmd), "rm -rf %s", s->smb_dir);
         ret = system(cmd);
         if (ret == -1 || !WIFEXITED(ret)) {
-            qemu_error("'%s' failed.\n", cmd);
+            error_report("'%s' failed.", cmd);
         } else if (WEXITSTATUS(ret)) {
-            qemu_error("'%s' failed. Error code: %d\n",
-                    cmd, WEXITSTATUS(ret));
+            error_report("'%s' failed. Error code: %d",
+                         cmd, WEXITSTATUS(ret));
         }
         s->smb_dir[0] = '\0';
     }
@@ -493,7 +493,7 @@
     snprintf(s->smb_dir, sizeof(s->smb_dir), "/tmp/qemu-smb.%ld-%d",
              (long)getpid(), instance++);
     if (mkdir(s->smb_dir, 0700) < 0) {
-        qemu_error("could not create samba server dir '%s'\n", s->smb_dir);
+        error_report("could not create samba server dir '%s'", s->smb_dir);
         return -1;
     }
     snprintf(smb_conf, sizeof(smb_conf), "%s/%s", s->smb_dir, "smb.conf");
@@ -501,8 +501,8 @@
     f = fopen(smb_conf, "w");
     if (!f) {
         slirp_smb_cleanup(s);
-        qemu_error("could not create samba server configuration file '%s'\n",
-                   smb_conf);
+        error_report("could not create samba server configuration file '%s'",
+                     smb_conf);
         return -1;
     }
     fprintf(f,
@@ -533,7 +533,7 @@
 
     if (slirp_add_exec(s->slirp, 0, smb_cmdline, &vserver_addr, 139) < 0) {
         slirp_smb_cleanup(s);
-        qemu_error("conflicting/invalid smbserver address\n");
+        error_report("conflicting/invalid smbserver address");
         return -1;
     }
     return 0;
@@ -618,14 +618,14 @@
     snprintf(buf, sizeof(buf), "guestfwd.tcp:%d", port);
     fwd->hd = qemu_chr_open(buf, p, NULL);
     if (!fwd->hd) {
-        qemu_error("could not open guest forwarding device '%s'\n", buf);
+        error_report("could not open guest forwarding device '%s'", buf);
         qemu_free(fwd);
         return -1;
     }
 
     if (slirp_add_exec(s->slirp, 3, fwd->hd, &server, port) < 0) {
-        qemu_error("conflicting/invalid host:port in guest forwarding "
-                   "rule '%s'\n", config_str);
+        error_report("conflicting/invalid host:port in guest forwarding "
+                     "rule '%s'", config_str);
         qemu_free(fwd);
         return -1;
     }
@@ -638,7 +638,7 @@
     return 0;
 
  fail_syntax:
-    qemu_error("invalid guest forwarding rule '%s'\n", config_str);
+    error_report("invalid guest forwarding rule '%s'", config_str);
     return -1;
 }