Fix db name with hypen issue

[kirtangajjar]

This PR fixes issue where if you specify a dbname with hyphen, you won't be able to create db. See - https://community.easyengine.io/t/cant-create-a-website-with-dbname-option/13926

What this PR does is, it replaces " with ' and wraps db name in backticks `.
i.e.

Before:

mysql -uroot -p"$MYSQL_ROOT_PASSWORD" -e"CREATE USER 'example.local-N4Ujuo'@'%' IDENTIFIED BY 'ZrNCJlx2KfsI'; CREATE DATABASE humo-gen; GRANT ALL PRIVILEGES ON humo-gen.* TO 'example.local-N4Ujto'@'%'; FLUSH PRIVILEGES;"

After:

mysql -uroot -p"$MYSQL_ROOT_PASSWORD" -e'CREATE USER "example.local-N4Ujuo"@"%" IDENTIFIED BY "ZrNCJlx2KfsI"; CREATE DATABASE `humo-gen`; GRANT ALL PRIVILEGES ON `humo-gen`.* TO "example.local-N4Ujto"@"%"; FLUSH PRIVILEGES;"

Also, I noticed in some cases when site creation fails and if /tmp/db_exec is not removed, site creation fails, so I've removed that file on site deletion.

Closes: EasyEngine/easyengine#1459

[mrrobot47]

LGTM