ZipFileRO: moar logging and wrap close

There is apparently still a race upon reading the entry Local File
Header that can't be tracked down, so move the LFH check inside the
mutex-protected block so we can call lseek again to see where we are
when we log an error.

Also, close() can fail so use TEMP_FAILURE_RETRY on it so we don't
unwittingly leak file descriptors when Mean Mr. EINTR comes a-knocking.

Change-Id: I753abad0bd882fe28f7281c406fa76f64393ef4c