autofs-5.0.8 - fix fix options compare

The change to fix the mount options compare replaced the strncmp()
function used to compare substrings of options with an internal
function that also used the passed in length for the compare.

But the case of a passed in length of 0 was not handled and for
that case the function returned a value different to strncmp()
and code that relied on that behaviour n longer behaves as expected.
autofs-5.0.8 - use open(2) instead of access(2)

The access(2) system call has been used to trigger dependednt automounts
in the target path when mounting. But access(2) no longer triggers the
dependednt mounts.

So use open(2) with flag O_DIRECTORY which will trigger these mounts.
autofs-5.0.8 - fix fix map source with type lookup

The recent change to make autofs look in the defined map directory
for map source file (or nss source files) when the map doesn't start
with a "/" broke the internal hosts map (thanks for alerting me to
this Leonardo).