Fixed test classpath to exclude JSch 0.1.46 bundled with Gradle.
Also fixed test cases.
Fixed JSch version for compile and test

This pull request fixes main and test classpath to exclude JSch 0.1.46 bundled with Gradle. All JSch version used for compile, test and plugin runtime will be same.

This pull request also fixes assertion of error message which is different between 0.1.46 and 0.1.50.