Fixed check for the existence of previous error log files.
Fixed check for the existence of previous error log files.

The '-f' parameter of test ie '[' expects a single file and seems to
error out on wildcards.
Solution found at
http://stackoverflow.com/questions/6363441/check-if-a-file-exists-with-wildcard-in-shell-script

FooDeas/raspberrypi-ua-netinst,yodaaut/raspbian-ua-netinst,racing-tech/rrp-raspi-installer,jturner314/raspbian-ua-netinst,cybercircuits/raspbian-ua-netinst,Zeerix/raspbian-ua-netinst,dicer/raspbian-ua-netinst,racing-tech/rrp-raspi-installer,kolargol/raspbian-ua-netinst,malsony/raspbian-ua-netinst,daytonpid/FireHawk,matt2005/raspbian-ua-netinst,beylsp/rpi-installer,beylsp/rpi-installer,firepick/FireHawk,bbinet/raspbian-ua-netinst