Revert "SE-988 Thread Safety issues in one of the constructors of default mule session."

This reverts commit 920d5640813940e549f8f5b59b2df50936ab01ac.

(cherry picked from commit 1c97afe0230a2e519b32bc3cd0845366a9d1c80e)

Conflicts:
	core/src/test/java/org/mule/processor/SedaStageInterceptingMessageProcessorTestCase.java