Clean-up: fix string truncation warning

Clean-up: fix string truncation warning

Some version of g++ emits the following warning:
  'char* strncpy(char*, const char*, size_t)' output may be truncated
  copying 255 bytes from a string of length 255 [-Wstringop-truncation]

Using the internal strncpy wrapper, which checks for truncation,
fixes the problem.

Change-Id: I8ab0f2cca0247eee329b137f547d3dfed32c995f
Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>