(SERVER-4) Eliminate direct file slurping

Slurp a FileInputStream rather than directly slurping the
/proc/meminfo file. This is due to a bug in OpenJDK wherein
the FileInputStream.available() method throws an exception when
called on a file in the /proc folder. Slurp a FileInputStream
rather than the file directly eliminates the call to this method.
I think it'd be good to add a comment that explains why we have to directly use `FileInputStream` here and links to that OpenJDK issue.