Don't run apexd in teardown if there is no apex.

If setup fails in the middle of mounting filesystems, it's possible that /system/bin/apexd exists but cannot be run (e.g., because /sys and /proc are not mounted yet). Running apexd in this case results in a crash, which is expected but can easily become a red-herring.

Bug: 311377497
Change-Id: Iaf8a201dd2dcbb8f17ae2ab16b285eac962c6ce4
Test: Presubmit
1 file changed