Only use limit.sh if /bin/bash executable, instead of if linux.

gute on irc just mentioned how his BusyBox server identifies as
linux but doesn't have bash installed. Additionally I see no
reason to limit limit.sh to linux, if for example somebody has
installed bash on a different *nix.

Change-Id: I51677295ab6bbc58fc5152106cf2c4c32bd1b0ea
Merge "Only use limit.sh if /bin/bash executable, instead of if linux."