ovs-pki: Reduce CA certificate validity to 10 years to fix 32-bit OpenSSL.

ovs-pki: Reduce CA certificate validity to 10 years to fix 32-bit OpenSSL.

Before I applied this commit, when I generated CA certificate with OpenSSL
0.9.8o on my 32-bit Debian system, I got a certificate that expired
sometime in 1977.  This made all SSL-based tests fail with an invalid
certificate.

32-bit time_t only extends to 2038, so this must be a bug in OpenSSL.
This commit works around the problem by reducing the validity period of
certificates to 10 years.

CC: Gurucharan Shetty <gshetty@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>