Redirect PyLammps stdout message

**Description of the error**
When PyLammps is initialised it prints the following to stdout:
```
LAMMPS (3 Mar 2020)
OMP_NUM_THREADS environment is not set. Defaulting to 1 thread. (src/comm.cpp:94)
using 1 OpenMP thread(s) per MPI task
LAMMPS output is captured by PyLammps wrapper
```

**Describe the expected result**
No message.

**Suggested fix**
Capture the output when PyLammps is initialised and redirect it to log.