Revert "Fixed YUMSTATUS variable as it was being set to the return code of mktemp instead of yum check-update"

This reverts commit f54225798e30ca44622a84c44c6428fbb09f1c2e.
Fixed YUMSTATUS variable and if statements

YUMSTATUS was always returning 0 due to being just after mktemp. Moved
to just after yum check-update.
The code for updates being available is 100 instead of 1 so I corrected
that. I also adjusted the syntax slightly.
Added logging, made email optional, updated email content

Removed email message when no updates are available as most people don't
want to be spammed by this. Added logic to only send the email when
there is one to send via the SENDEMAIL variable.
Added the hostname to the subject line
Adjusted wording of the message.
Added logging so that it is easy to monitor that the job has been
running and what the results were.
Corrected -Subject line, was set to MESSAGE instead of SUBJECT
Fixed syntax errors, adjusted indenting

Removed an extra fi on line 49
Added a missing then on line 52
Reduced indent of the main else block