Fix linux docker start

[linuxswords]

Adresses startup script for linux/docker users:

• fix volume mount
• changes permissions on solr_home for linux volume mount
• use more portable shebang

[sstults]

I agree with the portable shebang part, but the chown makes the directory unreadable from the image. Not sure why this difference exists between Mac and Linux. We could check uname and only do chown if it's not Mac.

[linuxswords]

@sstults Agreed and done on the uname and chown part. Added a hopefully clarifying comment and made the script pass shellcheck

[sstults]

Thank you @linuxswords this works perfectly. Merged.