RFR: 8266610: Method RandomAccessFile#length() returns 0 for block devices on linux.

[Vyom Tewari]

RandomAccessFile.length() method for block device return always 0

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Commit messages:
 - JDK-8266610: Method RandomAccessFile#length() returns 0 for block devices on linux.

Changes: https://git.openjdk.java.net/jdk/pull/3914/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=3914&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8266610
  Stats: 13 lines in 1 file changed: 10 ins; 2 del; 1 mod
  Patch: https://git.openjdk.java.net/jdk/pull/3914.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/3914/head:pull/3914

PR: https://git.openjdk.java.net/jdk/pull/3914