Revert "HACK: disable emulator on x86_64"

This reverts commit 4562c5bcb355c87a18e811ba8e6c2b6451a3ebf7.
Merge "Revert "HACK: disable emulator on x86_64""
Unset _JAVA_OPTIONS before running "java -version".

Unfortunately the previous approach of grepping out java version before
"head -n 1" clash with the effort of running "java -version" only once.

Change-Id: Ic78719c3bf1a54a45342d74bbbfa8e83bbc1bce1
Merge "Unset _JAVA_OPTIONS before running "java -version"."
auto-merger: merge in from aosp/master