net: http_server: Support HTTP1 405 error reply for all resource types

Reply with 405 Method not allowed not only for static FS resource types,
but also for others. Also, the method checking for for static resources
was messed up - those resource types only support GET by design, so no
need to compare resource method bitmask - it should be checked that the
request was actually GET instead.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>