kodev: correct "luarocks path bin" to "luarocks path --bin" and miscellaneous ShellCheck code quality issues
kodev: correct "luarocks path bin" to "luarocks path --bin" and miscellaneous ShellCheck code quality issues

References #2613

poire-z/koreader,koreader/koreader,Frenzie/koreader,NiLuJe/koreader,koreader/koreader,pazos/koreader,poire-z/koreader,apletnev/koreader,robert00s/koreader,Markismus/koreader,houqp/koreader,lgeek/koreader,mihailim/koreader,Frenzie/koreader,NiLuJe/koreader,Hzj-jie/koreader,mwoz123/koreader