Test fix csk roll

Multiple changes leading to csk_rollovers test not failed because of slow key generating. In the future we may use this for more tests where generating keys may cause timing problems. Eventually, the keys could be also generated in separate thread.

added 4 commits

• 36df0284 - keymgr: hidded option to generate a shared-policy key
• fa9ca08b - dnssec: fixed sharing KSK for alg roll and CSK
• 2eec47d6 - tests: added pre-generating keys with keymgr; csk-rollovers: RSA->ECDSA
• c07dea00 - dnssec: more accurate signing_scheme_present condition

Compare with previous version

merged

mentioned in commit 11a2a8bb