recovery: close zip archive after installation

Otherwise recovery will restart itself (gets killed by vold for
leaving a file open) when reboot is selected.

Change-Id: I915c3082bd99ca994c3a4cbe5ba913866051bc0e
recovery: Cleanups

 * Fixing warnings, const-correctness
 * Split the multi-call list out into recovery_cmds.h

 * This is part of an effort to improve security in recovery mode.

Change-Id: I1e913345c94537225639183434ea4803348ad335