virtiofsd: Add umask to seccom allow list

Patches in this series  are going to make use of "umask" syscall.
So allow it.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20210622150852.1507204-5-vgoyal@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

tools/virtiofsd/passthrough_seccomp.c

@@ -114,6 +114,7 @@ static const int syscall_allowlist[] = {
     SCMP_SYS(utimensat),
     SCMP_SYS(write),
     SCMP_SYS(writev),
+    SCMP_SYS(umask),
 };
 
 /* Syscalls used when --syslog is enabled */