usr_sbin/grml2ram: Fix a couple of shellcheck warnings

usr_sbin/grml2ram: Fix a couple of shellcheck warnings

- Ignore SC1091: Not following: /etc/grml/lsb-functions was not specified as input (see shellcheck -x).
- Ignore SC1091: Not following: /etc/grml/script-functions was not specified as input (see shellcheck -x).
- Set interpreter to /bin/bash because of SC2039: In POSIX sh, 'local' is undefined.
- SC2086: Double quote to prevent globbing and word splitting.
- SC2061: Quote the parameter to -name so the shell won't interpret it.
- SC2086: Double quote to prevent globbing and word splitting.
- SC2086: Double quote to prevent globbing and word splitting.
- SC2015: Note that A && B || C is not if-then-else. C may run when A is true.