BUG-731: StringBufferInputStream is deprecated

Change-Id: Idee23a2c94bd3e8cc1b4f8b656377f9fa087056c
Signed-off-by: Robert Varga <rovarga@cisco.com>
(cherry picked from commit 6a1672105828cf2c3ed52dbb26550b53c38403d2)
Signed-off-by: Robert Varga <rovarga@cisco.com>