[JENKINS-19192] Using JNR 3.0.1 which includes JNR-FFI 1.0.7; 1.0.6 has the...

[JENKINS-19192] Using JNR 3.0.1 which includes JNR-FFI 1.0.7; 1.0.6 has the backported fix for Guava #1505, the root cause.
So this upgrade ought to prevent a recurrence of the issue in case some other code refers to JNR from the CLI.
(As yet untested, and we do not especially want to send JNR over the CLI channel anyway for performance reasons.)