macos more tolerant than linux when writing to open file
macos more tolerant than linux when writing to open file

Signed-off-by: Zach Gershman <3025e35db44f20e0f186af1fead3044efb259b43@pivotal.io>

pivotal-cf-experimental/bosh-bootloader,niroyb/bosh-bootloader,pivotal-cf-experimental/bosh-bootloader,niroyb/bosh-bootloader