Add 'exit --wait-for-command' mode.

Add ability to exit tradefed only after all commands have been completed,
even those that have not been assigned a device yet.

Also add 'run cmdFileAndExit', which combines the 'run cmdFile' and
'exit -c' operations in a single statement.

Also deprecate the 'run singleCommand' syntax in favor of 'run commandAndExit'.

Bug 7978425

Change-Id: Id53010e4c6970b888b8eabee89cbc87385cf4f91
3 files changed