package/collectd: depend on luainterpreter for lua support

Since collectd lua support is compatible with any luainterpreter
implementation we should depend on BR2_PACKAGE_HAS_LUAINTERPRETER
instead of unconditionally selecting BR2_PACKAGE_LUA.

Signed-off-by: James Hilliard <james.hilliard1@gmail.com>
[yann.morin.1998@free.fr: use luainterpreter as dependency]
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>