Use output of rpm --eval command, in case import of rpm module fails

[mcyprian]

Order of the methods to get DEFAULT_PKG_SAVE_PATH is following:

• rpm Python API (should work on systems where is yum/dnf installed)
• rpm --eval command
• hardcoded path ~/rpmbuild (nonrpm environments e.g. travis)

Some functions from utils had to be moved elsewhere to prevent circular dependency between utils and settings modules.