Fix: illegal memory access in session_create

Found by Coverity:

CID 1323138 (#1 of 2): Buffer not null terminated
(BUFFER_SIZE_WARNING)3. buffer_size_warning: Calling strncpy with a
maximum size argument of 64 bytes on destination array session->hostname
of size 64 bytes might leave the destination string unterminated.

CID 1323138 (#2 of 2): Buffer not null terminated
(BUFFER_SIZE_WARNING)3. buffer_size_warning: Calling strncpy with a
maximum size argument of 255 bytes on destination array
session->session_name of size 255 bytes might leave the destination
string unterminated.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>