Fix hang on master=local

[dolfinus]

Using this connector with session created with .master("local[1]") hang because sparkContext.getExecutorMemoryStatus() always return 1, so guess is always 0, and while loop never ends. This was already reported in #14.

Added a check that if session created with .master("local") or .master("local[N]"), the value of sparkContext.defaultParallelism is returned:

• https://github.com/apache/spark/blob/v3.5.4/core/src/main/scala/org/apache/spark/SparkContext.scala#L2703
• https://github.com/apache/spark/blob/v3.5.4/core/src/main/scala/org/apache/spark/scheduler/TaskSchedulerImpl.scala#L1009
• https://github.com/apache/spark/blob/v3.5.4/core/src/main/scala/org/apache/spark/scheduler/cluster/CoarseGrainedSchedulerBackend.scala#L684-L686