vmm: seccomp: Add missing mremap() syscall

While testing self spawned vhost-user backends, it appeared that the
backend was aborting due to a missing system call in the seccomp
filters. mremap() was the culprit and this patch simply adds it to the
whitelist.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vmm/src/seccomp_filters.rs

@@ -224,6 +224,7 @@ pub fn vmm_thread_filter() -> Result<SeccompFilter, Error> {
             allow_syscall(libc::SYS_madvise),
             allow_syscall(libc::SYS_mmap),
             allow_syscall(libc::SYS_mprotect),
+            allow_syscall(libc::SYS_mremap),
             allow_syscall(libc::SYS_munmap),
             allow_syscall(libc::SYS_nanosleep),
             allow_syscall(libc::SYS_open),