When merging feature/v2 we have re-enabled the centos-minimal test
which has a blank line in the element-deps. The modified get_elements
functions added in If97bcd21e45de1b5ed91023fdc441a4617051a6b were not
handling this.
Fixing this, we can extract this into some common code for
element-deps and element-provides.
Also, I noticed while debugging that the element list is an iterator
from reverse(), so printing it doesn't help. Fix up the debug output.
Change-Id: I8e9b079f586e8a36dba3797a0fc03ca1b2041a04
19f13958f7