When reading the mtime from disk, the system can get a floating point
value. Convert this to an int for comparision purposes, else some
packages always get reindexed as the value in the index is an int.
(From OE-Core rev: cc01ffeee757738c169f8970fd89bf0933e93532)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>