Deactivate current env before activating new one

This is to address a bug where a currently active env would cause the
hpc init script to load the flepimop env not cleanly. Simplest solution
is to always deactivate before activating. Redundant in the case
that the flepimop env is already active, but easier than trying to
determine the current env. No downside if no env is active.

batch/hpc_init.sh

@@ -52,6 +52,7 @@ if [ -z "${FLEPI_CONDA}" ]; then
     fi
     echo "Using '$FLEPI_CONDA' for \$FLEPI_CONDA."
 fi
+conda deactivate
 conda activate $FLEPI_CONDA
 
 # Check the conda environment is valid