MSKP capture: write to a different directory

Writing to /data/user is no longer allowed, even with
`adb shell setenforce 0`. Write to /data/misc/mskps instead. Remove a
reference to the old location.

Attempt to create the file on device.

Bug: 296282988
Test: manual
Change-Id: I4565a1c7fd8b4e75cf2207c59bf76b45fd761ce1