SCTX-1766: Configurable timeout for stunnel

Imported from xen-api-libs-transitional.git
9e46fa5d7ae9c4d3f10e58fce968bcee91e5bbbc

Signed-off-by: Akshay <akshay.ramani@citrix.com>
Imported-by: John Else <john.else@citrix.com>
Merge pull request #159 from johnelse/ca-129196-xs64bit

SCTX-1766: Configurable timeout for stunnel