SUP-632 #populate the correct error when failing in execSftpCommand
print the output in case of error
SUP-632 #
Merge branch 'IX-9.2.0' into IX-9.1.0-SUP-632

fixed conflicts:
	infra/storage/file_transfer_managers/sftpMgr.class.php
Merge pull request #179 from kaltura/IX-9.1.0-SUP-632

Ix 9.2.0 sup 632