vmm: Add brk syscall to the API thread

The brk syscall is not always called as the system might not need it.
But when it's needed from the API thread, this causes the thread to
terminate as it is not part of the authorized list of syscalls.

This should fix some sporadic failures on the CI with the musl build.

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

vmm/src/seccomp_filters.rs

@@ -350,6 +350,7 @@ fn api_thread_rules() -> Result<Vec<SyscallRuleSet>, Error> {
     Ok(vec![
         allow_syscall(libc::SYS_accept4),
         allow_syscall(libc::SYS_bind),
+        allow_syscall(libc::SYS_brk),
         allow_syscall(libc::SYS_close),
         allow_syscall(libc::SYS_dup),
         allow_syscall(libc::SYS_epoll_create1),