Tramp fixes after running regression tests on Android

Tramp fixes after running regression tests on Android

* lisp/net/tramp-adb.el (tramp-adb-maybe-open-connection):
Unset environment variable PS2.

* lisp/net/tramp-androidsu.el (tramp-default-host-alist):
Don't add an entry; `tramp-default-host' is set properly.
(tramp-androidsu-maybe-open-connection): Don't set connection
property "remote-namespace" to nil, this is the default anyway.
Don't set connection property "remote-path", we use
connection-local values instead.  Unset environment variable PS2.
Dump shell options after setting all of them.
(tramp-androidsu-handle-make-process): Don't use hard-coded user "root".
(tramp-androidsu-connection-local-default-variables): New defvar.
Add it to connection-local profiles.