yum_helper: Put all yyoom logs into one file

Since yyoom now writes a dates and logs start and end of its execution
to its log file (if one provided), and also does not overwrite it but
amends to it instead it makes more sense to write all yyoom logs to one
log file instead of spreading them into different log file per command
type.

Change-Id: I718c89a48f6629cc585876f6dab2a46d2d5035e0
Merge "yum_helper: Put all yyoom logs into one file"