kt: allow use of kubernetes pki file paths transparently
kt: allow use of kubernetes pki file paths transparently

Certificates can be in different paths depending on what is managing them.
While it is possible to make kubernets to relocate paths to match with what
this library expects, it is much nicer if the library can search for well
known file paths.  I admit, this is purely convenience.

Signed-off-by: Sami Kerola <419b943ff7c1ed3563aaadac6fd0f9f385aec08a@iki.fi>

cloudflare/golibs,cloudflare/golibs,cloudflare/golibs