refactor: Reuse logic from common functions

From @MaxymVlasov in antonbabenko#401 (comment):
> Heh, you found code written in Paleolithic.
>
> Let's try reuse logic that used in common functions here:
>
> https://github.com/antonbabenko/pre-commit-terraform/blob/master/hooks/_common.sh#L178
>
> Absolutely have no idea why it was written in so complex way

Author: nshenry03

hooks/terraform_validate.sh

@@ -111,7 +111,7 @@ function terraform_validate_ {
 
     if [[ -n "$(find "$dir_path" -maxdepth 1 -name '*.tf' -print -quit)" ]]; then
 
-      pushd "$(cd "$dir_path" > /dev/null && pwd -P)" > /dev/null
+      pushd "$dir_path" > /dev/null || continue
 
       if [ ! -d .terraform ]; then
         set +e