jailer: add metric for seccomp faults
jailer: add metric for seccomp faults

These metrics will be incremented in the signal handler for SIGSYS, which
is sent by the kernel when a blacklisted syscall is attempted.
- bad_syscalls is a map syscall number -> number of times it was attempted
- num_faults is the total number of syscalls that were denied by the
  kernel

Signed-off-by: Alexandra Iordache <750ec4522de000f31ad44d64614ad5747f238032@amazon.com>

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