ARROW-2589: [CI] Avoid Pandas 0.23.0

There is a regression (*) in Pandas 0.23.0 that breaks test_parquet.py.
Pin to 0.22.0 until the issue gets fixed upstream.

(*) pandas-dev/pandas#21083

Author: pitrou

ci/cpp-python-msvc-build.bat

@@ -68,8 +68,9 @@ if "%JOB%" == "Build_Debug" (
   exit /B 0
 )
 
+@rem Pandas pinned to 0.22.0 because of regression in 0.23.0 (ARROW-2589)
 conda create -n arrow -q -y python=%PYTHON% ^
-      six pytest setuptools numpy pandas cython ^
+      six pytest setuptools numpy pandas=0.22.0 cython ^
       thrift-cpp=0.11.0
 
 call activate arrow

ci/travis_script_python.sh

@@ -36,11 +36,12 @@ source activate $CONDA_ENV_DIR
 python --version
 which python
 
+# Pandas pinned to 0.22.0 because of regression in 0.23.0 (ARROW-2589)
 conda install -y -q pip \
       nomkl \
       cloudpickle \
       numpy=1.13.1 \
-      pandas \
+      pandas=0.22.0 \
       cython
 
 # ARROW-2093: PyTorch increases the size of our conda dependency stack