[metal] Ensure that we clean up command buffer even on failure.
[metal] Ensure that we clean up command buffer even on failure.

When we failed to commit, we were keeping the old command buffer around
which could lead to issues if we tried to use it later.

Change-Id: I7397735931c49d5383490bbc213059bd42d2ea84
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/467777
Reviewed-by: Greg Daniel <39df0a804564ccb6cf75f18db79653821f37c1c5@google.com>
Commit-Queue: Jim Van Verth <509afb0bfbb23ecaaf1fb3323209f531b45e75a6@google.com>

aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia