transfer.py: Add proper error message at source/target split of option_parse

The option_parse function gives IndexError exception when the source/target
does not follow hostname:path pattern. This patch adds a proper error message
and system exit to the non proper source/destination arguments. This helps the
user to understand the exact mistake while using this framwork.

Bug: T253560
Change-Id: I3292754833cf0b63efbe7b9f7484c296d34a6e7b