Add libssh2-1 to ubuntu-trusty; resolves travis-ci/apt-package-whitelist#3807
Add libssh2-1 to ubuntu-trusty; resolves travis-ci/apt-package-whitelist#3807

Packages: libssh2-1 libssh2-1-dev libssh2-1-dbg

travis-ci/apt-package-whitelist,travis-ci/apt-package-whitelist