Fix test failures with -Xjitthreshold:0.

Namely
  - 667-jit-jni-stub:
    fix GenericJNI to respect -Xjitthreshold:0,
  - 1935-get-set-current-frame-jit:
    check for OSR, not for being interpreted.
However, some failures remain when --gcstress is added.

Test: testrunner.py --host --jit --runtime-option=-Xjitthreshold:0
Test: testrunner.py --host
Bug: 62611253
Change-Id: I4ca880f6a8b64a1659a27a107fae9933d4174f8d