RFR: JDK-8214710 Fix hg log in update_copyright_year.sh

[Magnus Ihse Bursie]

The commands for hg log is missing -l1, which will limit the log to just 
the revision specified. Instead, all revisions from repo creation will 
now be included, and the script fails to work.

I will publish a separate changeset with missed copyright year updates 
in the build system.

Bug: https://bugs.openjdk.java.net/browse/JDK-8214710
WebRev: 
http://cr.openjdk.java.net/~ihse/JDK-8214710-fix-update-copyright-year/webrev.01

/Magnus