Stop running gltestpersistentcache in PreAbandonContext mode

The config fails to initialized in push_sinks because readbacks in test
draw don't match (as the GrContext is already in abandoned mode).

Change-Id: I73c68ab52df3e83b688ab43fbe74cf4c1ae8c19d
Reviewed-on: https://skia-review.googlesource.com/141562
Auto-Submit: Brian Salomon <bsalomon@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
2 files changed