PCPCombine forecast tasks have incorrect check for obs dir

[mkavulich]

Expected behavior

PCP combine tasks that combine forecast data should not have a dependency on observation files.

Current behavior

Currently if the get_obs tasks do not finish in time, PCP combine forecast tasks for e.g. APCP will fail due to the observations missing, despite those obs not being necessary. This happens starting at line 292 in scripts/pcpcombine.sh:

#-----------------------------------------------------------------------
#
# Check for existence of top-level OBS_DIR.
#
#-----------------------------------------------------------------------
#
if [ ! -d "${OBS_DIR}" ]; then
  print_err_msg_exit "\
OBS_DIR does not exist or is not a directory:
  OBS_DIR = \"${OBS_DIR}\""
fi

Steps To Reproduce

This is a bit difficult to reproduce as it depends on the machine timing for submissions of specific tasks. But it can often be replicated by running "all" WE2E tests at once; this tends to slow down the get_obs tasks that retrieve obs from HPSS and allow this problem to manifest.

Detailed Description of Fix

Enclose the above code with an if [ "${FCST_OR_OBS}" = "OBS" ]; then statement

[mkavulich]

Resolved via #25