Squashed adb fixes.

fix up adb to prefer /sbin/sh if it exists

allow always insecure

Change-Id: I5c15731c95d123488e90aaeac5b497f556b53363

Conflicts:

	adb/Android.mk
adbd: Disable "adb root" by system property (2/3)

 * Require persist.sys.root_access=1 on non-eng debuggable builds

Change-Id: Iedab030e81ffb525fed64aed80cf0014f3e07073