Fixing the static tests script for zsh

Summary:
Adding more fixes for zsh. Fixed allscripts variable to correctly list
all the files. zsh does not allow filename expansion in variable
evaluation by defualt. Also git grep needs the GIT_PAGER to be unset
explicitly in zsh.

Test Plan:
static_tests.sh should complete without errors or going in to
a pager in both zsh and bash.

Reviewers: jevripio

Reviewed By: jevripio

CC: phab

Differential Revision: https://sibld.phab.dev.bloomberg.com/D134