[SPARK-20064][PYSPARK] Bump the PySpark verison number to 2.2

## What changes were proposed in this pull request?
PySpark version in version.py was lagging behind
Versioning is  in line with PEP 440: https://www.python.org/dev/peps/pep-0440/

## How was this patch tested?
Simply rebuild the project with existing tests

Author: setjet <rubenljanssen@gmail.com>
Author: Ruben Janssen <rubenljanssen@gmail.com>

Closes #17523 from setjet/SPARK-20064.

python/pyspark/version.py

@@ -16,4 +16,4 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-__version__ = "2.1.0.dev0"
+__version__ = "2.2.0.dev0"