travis: add libssl-dev
travis: add libssl-dev

It is needed in integ test for hash calculation.

Signed-off-by: Tadeusz Struk <ac7da5bc34fbda078ba4af5ef710d2a59a2316f5@intel.com>

tpm2-software/tpm2-tss,tpm2-software/tpm2-tss,01org/TPM2.0-TSS,01org/TPM2.0-TSS,01org/TPM2.0-TSS,01org/tpm2-tss,01org/tpm2-tss,tpm2-software/tpm2-tss,01org/TPM2.0-TSS,01org/tpm2-tss